{"1": {"fulltext": "", "height": "3915", "width": "2500", "jp2-path": "refractionhowtor00thor_0001.jp2"}, "2": {"fulltext": "LIBRARY OF CONGRESS.\\nChap. Copyright No..\u00e2\u0080\u0094.\\nShelf]\\nUNITED STATES OF AMERICA.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0002.jp2"}, "3": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0003.jp2"}, "4": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0004.jp2"}, "5": {"fulltext": "REFRACTION\\nAND\\nHOW TO REFRACT\\nTHORINGTON", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0005.jp2"}, "6": {"fulltext": "BY THE SAME AUTHOR.\\nRetinoscopy (The Shadow Test) in the Determination\\nof Refraction at One Meter Distance with the Plane\\nMirror. 38 Illustrations, a number of which are in\\nColors. Third Edition. Cloth, net, $i.co\\nFrom The Medical Record, New York.\\nIt presents a clear, terse, and thorough exposition of an\\nobjective method of determining refraction errors which is de-\\nservedly increasing in popularity. In our opinion the author is\\namply justified in declaring that its great value in nystagmus, young\\nchildren, amblyopia, aphakia, and in examining illiterates and the\\nfeeble minded, cannot be overestimated, and we agree with him in\\nreminding those who attempt retinoscopy, fail, and ridicule it, that\\nthe fault is behind and not in front of the mirror. The book is well\\nprinted and usefully illustrated.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0006.jp2"}, "7": {"fulltext": "REFRACTION\\nAND\\nHOW TO REFRACT\\nINCLUDING SECTIONS ON OPTICS, RETINOSCOPY, THE\\nFITTING OF SPECTACLES AND EYE-GLASSES, ETC.\\nBY\\nJAMES THORINGTON, A.M., M.D.,\\nPROFESSOR OF DISEASES OF THE EYE IN THE PHILADELPHIA POLYCLINIC AND COLLEGE\\nFOR GRADUATES IN MEDICINE ASSOCIATE MEMBER OF THE AMERICAN\\nOPHTHALMOLOGICAL SOCIETY; FELLOW OF THE COLLEGE\\nOF PHYSICIANS OF PHILADELPHIA, ETC.\\nSeconD Bfcition\\nTWO HUNDRED ILLUSTRATIONS\\nTHIRTEEN OF WHICH ARE COLORED\\nPHILADELPHIA\\nP. BLAKISTON S SON CO\\nIOI2 WALNUT STREET\\nI 900", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0007.jp2"}, "8": {"fulltext": "49415\\nSEP 19 1900\\nGKG\u00c2\u00a34tfVl90ll.\\nSEP 24 1900\\nv\\n8019a\\nCopyright, 1899, by P. Blakiston s Son Co.\\nCopyright, 1900, by P. Blakiston s Son Co.\\nWM. F. FELL CO.,\\nElectrotypers and Printers,\\n1220-24 sansom street. philadelphia.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0008.jp2"}, "9": {"fulltext": "PREFACE.\\nThis book has been written at the request of the many\\nstudents who have attended the author s lectures on\\nRefraction at the Philadelphia Polyclinic; and while it\\nis intended for all beginners in the study of Ophthalmology,\\nyet it is especially for those practitioners and students who\\nmay have a limited knowledge of mathematics and who can\\nnot readily appreciate the classic treatise of Donders.\\nIn the preparation of the manuscript and in arranging these\\npages the writer has planned to be systematic and practi-\\ncal, so that the student, starting with the consideration of\\nrays of light, is gradually brought to a full understanding\\nof optics and following this, he is taught what is the stan-\\ndard eye, and then is given a description of ametropic eyes,\\nwith a differential diagnosis of each, until finally he is told\\nhow to place lenses in front of ametropic eyes to make\\nthem equal to the standard condition.\\nBy being dogmatic rather than ambiguous, with occa-\\nsional repetitions to avoid frequent references, and by simple\\nexplanations and a definite statement of facts, the writer has\\naimed to make the text more concise and comprehensive\\nthan if encumbered with lengthy mathematic formulas or\\nwith any discussion of disputed points.\\nThe chapter on Retinoscopy embraces descriptions of that\\nmethod of refracting, both with the plane and with the\\nconcave mirror but no matter how carefully expressed, the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0009.jp2"}, "10": {"fulltext": "VI PREFACE.\\nstudent will frequently confuse the two, and he is therefore\\nreferred to the author s manual on Retinoscopy with the\\nPlane Mirror.\\nOf the two hundred illustrations used to elucidate this\\nwork, nearly all are newly made, and were drawn or photo-\\ngraphed by the author. Those in colors, on page 145, and\\nthe diagrams of astigmatic eyes, as also several others, are\\noriginal.\\nThe author desires to tender his thanks to Dr. Helen\\nMurphy, of Philadelphia, and to Dr. J. Ellis Jennings, of\\nSt. Louis, Mo., for many valuable suggestions.\\n120 S. 1 8th St., Philadelphia, Pa.\\nNovember, i8gg.\\nPREFACE TO SECOND EDITION\\nThe first edition of this work was published in November,\\n1899, and it is indeed gratifying to the author that the work\\nhas found such favor as to call for a second in so short a\\ntime.\\nIn preparing this edition and to make it more lucid than\\nthe first, the writer has carefully reviewed the original text\\nand made some changes in the phraseology.\\nThe writer takes this opportunity to thank his many\\nfriends and correspondents, at home and abroad, for their\\ncomplimentary letters and reviews, which are gratefully\\nappreciated.\\nSeptember, igoo.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0010.jp2"}, "11": {"fulltext": "CONTENTS.\\nCHAPTER I.\\nPAGE\\nOptics, 9\\nCHAPTER II.\\nThe Eye. The Standard Eye. The Cardinal Points. Vis-\\nual Angle. Minimum Visual Angle. Standard Acute-\\nness of Vision. Size of Retinal Image. Accommodation.\\nMechanism of Accommodation. Far and Near Points.\\nDetermination of Distant Vision and Near Point.\\nAmplitude of Accommodation. Convergence. Angle\\nGamma. Angle Alpha, 58\\nCHAPTER III.\\nOphthalmoscope. Direct and Indirect Methods, 86\\nCHAPTER IV.\\nEmmetropia. Hyperopia. Myopia, 101\\nCHAPTER V.\\nAstigmatism, or Curvature Ametropia. Tests for Astigma-\\ntism, 120\\nCHAPTER VI.\\nRetinoscopy, 154\\nCHAPTER VII.\\nMuscles, 172\\nCHAPTER VIII.\\nCycloplegics. Cycloplegia. Asthenopia. Examination of\\nthe Eyes, 200\\nvii", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0011.jp2"}, "12": {"fulltext": "Vlll CONTENTS.\\nCHAPTER IX.\\nPAGE\\nHow to Refract, 220\\nCHAPTER X.\\nApplied Refraction, 233\\nCHAPTER XI.\\nPresbyopia. Aphakia. Anisometropia. Spectacles, 260\\nCHAPTER XII.\\nLenses, Spectacles, and Eye-glass Frames. How to Take\\nMeasurements for Them and How They Should be\\nFitted, 285\\nINDEX, 295", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0012.jp2"}, "13": {"fulltext": "LIST OF ILLUSTRATIONS.\\n~IG. PAGE\\n1. Reflection, 12\\n2. Reflection from Plane Mirror, 12\\n3. Lateral Inversion, 13\\n4. Reflection from Concave Mirror, 14\\n5. Erect Image Formed by Concave Mirror, 15\\n6. Inverted Image Formed by Concave Mirror, 16\\n7. Image Formed by Convex Mirror, 17\\n8. Perpendicular to Plane Surfaces, 18\\n9. Refraction, 18\\n10. Critical Angle, 19\\n11 and 12. Angle of Refraction, 20\\n13. Density, 20\\n14. Index of Refraction, 21\\n15. Maximum Deviation, 22\\n16. Minimum Deviation, 22\\n17. Angle of Deviation, 23\\n18. Displacement, 24\\n19. Centrad, 24\\n20. Prism Diopter, 24\\n21. Neutralization of Prisms, 25\\n22. Correction of Diplopia, 28\\n23. 24, and 25. Convex Lenses, 29\\n26, 27, and 28. Concave Lenses, 30\\n29. Peripheral Refraction Through a Convex Lens, 30\\n30. Peripheral Refraction Through a Concave Lens, 30\\n31. Parallel Rays Passing Through a CorfVex Lens, 31\\n32. Parallel Rays Passing Through a Concave Lens, 32\\n33. Conjugate Foci, 33\\n34. Ordinary Foci, 34\\n35. Negative Focus, 35\\n36. Secondary Axes, 35\\n37. Optic Center, 36\\n38. Inverted Image Formed by a Convex Lens, 37\\n39. Erect Magnified Image Formed by a Convex Lens, 39\\n40. Image Formed by a Concave Lens, 39\\n41 and 42. Cylindric Lenses, 43\\n43. Cylinder Axis, 43\\n44. Parallel Rays Passing Through a Convex Cylinder, 43\\n45- Parallel Rays Passing Through a Concave Cylinder, 44\\n46. Trial -case, 45\\nix", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0013.jp2"}, "14": {"fulltext": "LIST OF ILLUSTRATIONS.\\nFIG. PAGE\\n47 and 48. Trial- frames, 46 and 47\\n49. Combining Sphere and Cylinder, 49\\n50, 51, and 52. Finding Optic Center of a Lens, 54\\n53 and 54. Finding Cylinder-axis, 55\\n54, 55, and 56. Action of a Cylinder, 55 and 56\\n57. Standard Eye, 59\\n58. Angle of View, 60\\n59 and 60. Size of Retinal Image, 61\\n61. Minimum Visual Angle, 62\\n62 and 63. Five-minute Angle, 63\\n64. Retinal Image in the Standard and Ametropic Eyes, 64\\n65. Crystalline Lens at Rest and Accommodating, 67\\n66. Accommodation, 68\\n67. Hyperopic Eye at Rest, 70\\n68. Myopic Eye at Rest, 71\\n69. Randall s Test-letters, 73\\n70. Wallace Test-letters, 74\\n71. Illiterate Card, 74\\n72. Gould s Test-letters, 75\\n73. Gothic Type for Testing Near Point, 79\\n74. Block Letters for Testing the Near Point, 80\\n75. Meter Angle of Convergence, 82\\n76. Angle Gamma, 83\\n77. Positive Angle Gamma, 84\\n78. Negative Angle Gamma, 85\\n79. Loring Ophthalmoscope, 87\\n80. Direct Ophthalmoscopy, I 88\\n81. Emmetropia with the Ophthalmoscope, 94\\n82. Hyperopia with the Ophthalmoscope, 95\\n83. Myopia with the Ophthalmoscope, 96\\n84. Indirect Ophthalmoscopy, 98\\n85. Condensing Lens, 98\\n86. Emmetropia, 101\\n87. Emmetropic and Ametropic Eyes 23 mm. Long, 102\\n88. Hyperopic Eye at Rest, 105\\n89. Hyperopic Eye Refracted, 105\\n90. Parallel Rays Entering a Myopic Eye no\\n91. Myopic Eye at Rest, in\\n92. Myopic Eye Refracted, in\\n93. Astigmatic Lens, 121\\n94. Simple Hyperopic Astigmatism, 124\\n95. Simple Myopic Astigmatism, 125\\n96. Compound Hyperopic Astigmatism, 125\\n97. Compound Myopic Astigmatism, 126\\n98 and 99. Mixed Astigmatism, 127\\n100. Symmetric Astigmatism, 128\\n101. Asymmetric Astigmatism, 128\\n102. Astigmatism with the Rule, 129\\n103. Astigmatism Against the Rule, 129\\n104. Placido s Disc, 133\\n105. Stenopeic Slit, 133\\n106. Green s Astigmatic Chart, 135", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0014.jp2"}, "15": {"fulltext": "LIST OF ILLUSTRATIONS. XI\\nFIG. PAGE\\n107. Astigmatic Clock-dial, 136\\n108. Astigmatic Clock-dial in Black, 137\\n109. Author s Pointed Line Test, 139\\nno. Perforated Disc, 140\\nin. Pray s Letters, 140\\n112. Scheiner s Disc, 141\\n113. Scheiner s Disc in Hyperopia, 141\\n114. Scheiner s Disc in Myopia, 142\\n115 and 116. Cobalt-blue Glass, 143\\n117. Refrangibility of Cobalt-blue Glass, 144\\n118 to 129, inclusive. The Diagnosis of the Different Forms of Ametro-\\npia with Cobalt-blue Glass, 145\\n130. Thomson s Ametrometer, 147\\n131 and 132. Ophthalmometer, 148 and 149\\n133 and 134. Mires or Targets, 150\\n135. Indirect Ophthalmoscopy, 153\\n136. Author s Schematic Eye, 154\\n137. Point of Reversal, 155\\n138 and 139. Author s Mirror with Folding Handle, 156\\n140. Author s Iris Diaphragm Chimney, 157\\n141. Position of Light and Minor, 158\\n142. High Myopia as Seen with the Concave Minor, 159\\n143. Hyperopia as Seen with die Concave Mirror, 159\\n144 and 145. Rate of Movement of Retinal Illumination in Hyperopia\\nand Myopia, 162 and 163\\n146. Retinal Illumination in Emmetropia, 164\\n147. Band of Light, 167\\n148. Axonometer, 168\\n149. Scissor Movement, 170\\n150. Positive Aberration, 171\\n151. Negative Aberration, 171\\n152. Homonymous Diplopia, 173\\n153. Heteronymous Diplopia, 174\\n154 and 155. Maddox Rods, 182\\n156. Rotary Prism of Risley, 183\\n157. Phorometer, 184\\n158. Strabismometer, 194\\n159. Angle of Deviation in Strabismus, 195\\n160. Monocular Blinder, 197\\n161. Aphakia, 267\\n162 and 163. Franklin Bifocals, 273\\n164. Morck s Bifocals, 273\\n165 to 171, inclusive. Cement Bifocals, 274 and 275\\n172 and 173. Acromatic Bifocals, 275\\n174 and 175. Solid Bifocals, 276\\n176 to 180, inclusive. Half Lenses, 277\\n181. Toric Lenses, 278\\n182 to 191. inclusive. Different Sizes and Shaped Lenses, 283 and 286\\n192. Measuring Interpupillary Distance, 289\\n193 and 194. Fitting of Spectacle Bridge, 290\\n195. Measurement of Bridge, 291\\n196. Measurement for Spectacles, 292", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0015.jp2"}, "16": {"fulltext": "Xll LIST OF ILLUSTRATIONS.\\nFIG. PAGE\\n197. Measurement for Eye-glasses, 292\\n198. Distance Frames, 293\\n199. Near Frames, 293\\n200. Measurement for Guards, 293", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0016.jp2"}, "17": {"fulltext": "REFRACTION\\nHOW TO REFRACT.\\nCHAPTER I.\\nOPTICS.\\nOptics (from the Greek o-ro/iac, meaning to see is\\nthat branch of physical science which treats of the nature\\nand properties of light.\\nCatoptrics (from the Greek xdronzpov, meaning a mir-\\nror and dioptrics (from the Greek d( --pov, meaning\\nto see through are subdivisions of optics the former\\ntreating of incident and reflected rays, and the latter of the\\nrefraction of light passing through different media, such as\\nair, water, glass, etc., but especially through lenses.\\nLight. Light may be defined as that form of energy\\nwhich, acting upon the organs of sight, renders visible the\\nobjects from which it proceeds. This form of energy is\\npropagated in waves in all directions from a luminous body,\\nand with a velocity in a vacuum of about 186,000 miles a\\nsecond. In the study of a luminous body, such as a candle-,\\nlamp-, or gas-flame, the substance itself must not be con-\\nsidered as a single source of radiation, but as a collection\\nof minute points, from every one of which waves proceed\\nin all directions and cross one another as they diverge from\\ntheir respective points. The intensity of light decreases\\n9", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0017.jp2"}, "18": {"fulltext": "IO REFRACTION AND HOW TO REFRACT.\\nas the square of the distance from the light increases for\\nexample, if an object is twice as far from a luminous body\\nas another of the same size, it will receive one-fourth as\\nmuch light as the latter.\\nRay. Ray (from radius is used in optics in prefer-\\nence to wave, and means the smallest subdivision of light\\ntraveling in a straight line. Rays of light are considered\\nas incident, emergent, reflected, refracted, divergent, par-\\nallel, and convergent.\\nIncident Rays. Rays of light are said to be incident\\nwhen they strike the surface of an object.\\nEmergent Rays. Rays of light are emergent when\\nthey have passed through a transparent substance.\\nReflected Rays. Rays of light are reflected when they\\nrebound from a polished surface.\\nRefracted Rays. A ray of light undergoes refraction\\nwhen it is deviated from its course in passing through any\\ntransparent substance.\\nDivergent Rays. Rays of light proceed divergently\\nfrom any luminous substance, but, in the study of refrac-\\ntion, only those which proceed from a point closer than six\\nmeters are spoken of as divergent.\\nParallel Rays. The greater the distance of any lumin-\\nous point, the more nearly do its rays approach to paral-\\nlelism this is evident in a study of rays coming from such\\ndistant sources as the sun, moon, and stars. For all prac-\\ntical purposes in the study of refraction, rays of light which\\nproceed from a distance of six meters or more are spoken of\\nas parallel, although this is not an absolute fact, as rays of\\nlight at this distance still maintain a slight amount of diver-\\ngence. If the pupil of the emmetropic eye is represented\\nby a circular opening four millimeters in diameter, then\\nrays of light from a luminous point at six meters (6000", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0018.jp2"}, "19": {"fulltext": "OPTICS. I I\\nmm.) will have a divergence of ^qq when they enter such\\na pupil.\\nConvergent Rays. Convergent rays are the result of\\nreflection from a concave mirror or refraction through a\\nconvex lens.\\nA Beam. This is a collection or series of parallel rays.\\nA Pencil. A pencil of light is a collection of conver-\\ngent or divergent rays. Convergent rays are those which\\ntend to a common point, whereas divergent rays are those\\nwhich proceed from a point and continually separate as they\\nproceed. This point is called the radiant point.\\nA Focus. This is the point of a convergent or diver-\\ngent pencil the center of a circle the point to which\\nconverging rays are directed.\\nA Positive or Real Focus. This is the point to which\\nrays are directed after passing through a convex lens or\\nafter reflection from a concave mirror.\\nA Negative or Virtual Focus. This is the point from\\nwhich rays appear to diverge after passing through a con-\\ncave lens, or after reflection from a convex mirror, or after\\nrefraction through a convex lens when the light or object is\\ncloser to the lens than its principal focus, or after reflection\\nfrom a concave mirror when the light or object is closer to\\nthe mirror than its principal focus.\\nThe principal phenomena of light are absorption, reflec-\\ntion, and refraction.\\nAbsorption. Rays of light from the sun falling upon\\nthe green grass are partly absorbed and partly reflected.\\nThe grass absorbs some of the rays and sends back or\\nreflects only those rays which together produce the effect of\\ngreen. A piece of red glass owes its color to the fact that\\nit transmits only that portion of the light s rays whose\\ncombined effect upon the retina is that of red. The relative", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0019.jp2"}, "20": {"fulltext": "12\\nREFRACTION AND HOW TO REFRACT.\\nproportion of absorption and reflection of rays of light\\ngreatly depends upon the quality of the surface whether\\nlight colored or polished, or dark colored or rough.\\nReflection. From the Latin reflectere, to rebound.\\nThis is the sending back of rays of light by the surface on\\nwhich they fall into the medium through which they came.\\nWhile most of the rays falling upon the surface of a trans-\\nparent substance pass through it, with or without change\\nin their direction, yet some of the rays are reflected, and it\\nis by these reflected rays that surfaces are made visible.\\nFig. 2.\\nA substance that could transmit or absorb all the rays of\\nlight coming to it (if such a substance existed) would be\\ninvisible. Reflection, therefore, always accompanies refrac-\\ntion, and, if one of these disappear, the other will disappear\\nalso.\\nLaws of Reflection. (i) The angle of reflection is\\nequal to the angle of incidence. (2) The reflected and in-\\ncident rays are in the same plane with the perpendicular to\\nthe surface. (See Fig. 1.)\\nIf A B represent a polished surface and I the incident\\nray, then P D I is the angle of incidence R being the re-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0020.jp2"}, "21": {"fulltext": "OPTICS.\\n13\\nfleeted ray, then P D R, equal to it, is the angle of reflection.\\nI D, P D, and R D lie in the same plane.\\nA reflecting surface is usually a polished surface (a\\nmirror), and may be plane, concave, or convex.\\nReflection from a Plane Mirror. Rays of light are\\nreflected from a plane mirror in the same direction in which\\nthey fall upon it if parallel, convergent, or divergent be-\\nfore reflection, then they are parallel, convergent, or diver-\\ngent after reflection. An object placed in front of a plane\\nmirror appears just as far back in the mirror as the object\\nis in front of it. (See\\nFig. 2.)\\nA B represents a plane\\nmirror with E F, rays\\nfrom the extremes of the\\nobject I, reflected from\\nthe mirror A B, and meet-\\ning at the observer s eye\\nas if they came from the\\nobject I in the mirror.\\n(See Visual Angle, p.\\n60.) The apparent dis-\\ntance of the object I from the observer is equal to the\\ncombined length of the incident and reflected rays.\\nThe appearance of an image in a plane mirror is not\\nexactly the same as that of the object facing the mirror\\nit undergoes what is known as lateral inversion. This is\\nbest understood by holding a printed page in front of a\\nplane mirror, when the words or letters will read from right\\nto left. (See Fig. 3.) An observer facing a plane mirror\\nand raising his right hand, his image apparently raises the\\nleft hand.\\nTilting a plane mirror gives an object the appearance of\\nR\\nr^\\nE F\\n1 3\\nLEC\\n03J\\nTION\\nl/IOIT\\nFig. 3. Lateral Inversion.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0021.jp2"}, "22": {"fulltext": "14\\nREFRACTION AND HOW TO REFRACT.\\nmoving in the opposite direction to that in which the mirror\\nis tilted.\\nSpheric Mirrors. A spheric mirror is a portion of a\\nreflecting spheric surface its center of curvature is therefore\\nthe center of the sphere of which it is a part. Spheric mir-\\nrors are of two kinds concave and convex.\\nReflection from a Concave Mirror (Fig. 4). Parallel\\nrays are reflected from a concave mirror, and are brought to\\na focus in front of it. This point is called the principal focus\\n(P.F.). The principal axis of a concave mirror is a straight\\nline drawn from the mirror through the principal focus and\\nFig. 4.\\nthe center of curvature (i-i), and a secondary axis (2 2\\n2 2 r is any other straight line passing from the mirror to\\nthe center of curvature (C.C.). Rays which diverge from\\nany point beyond the principal focus are reflected con-\\nvergently (G J). Rays which diverge from any point closer\\nthan the principal focus are reflected divergently (V V).\\nImages Formed by a Concave Mirror. To find the\\nposition of an image as formed by a concave mirror, two\\nrays may be used one drawn from a given point on the\\nobject to the mirror, and parallel to its principal axis, and\\nreflected through the principal focus (P.F., Figs. 5 and 6)\\nthe other, the secondary axis, from the same point, passing", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0022.jp2"}, "23": {"fulltext": "OPTICS.\\n15\\nthrough the center of curvature. The place where the\\nsecondary axis and the reflected ray or their projections in-\\ntersect gives the position of the image. Unlike the plane\\nmirror, which produces images at all times and at all dis-\\ntances, the concave mirror produces either an erect, virtual,\\nand enlarged image, as an object is placed closer than its\\nprincipal focus, or an enlarged inverted image if the object\\nis between the principal focus and the center of curvature.\\nBy withdrawing the mirror in the former instance the\\nerect image increases slightly in size, and in the latter the\\ninverted image diminishes in size. At the principal focus\\nthere is no image formed.\\nFig. 5.\\nFigure 5 shows an erect, virtual, and enlarged image of\\nA R which is closer to the mirror than the principal focus.\\nParallel rays from A and R are reflected to the principal\\nfocus, P.F. Lines drawn from the center of curvature\\nthrough A and R to the mirror are secondary axes these\\nlines and those reflected to the principal focus do not inter-\\nsect in front of the mirror, but if projected, will meet at a\\nand r behind the mirror, forming a magnified image of\\nA R. If the mirror is withdrawn from the object, the\\nerect magnified image will increase in size, but at the prin-\\ncipal focus no image will be formed, as the rays are reflected\\nparallel.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0023.jp2"}, "24": {"fulltext": "ID REFRACTION AND HOW TO REFRACT.\\nFigure 6 shows a real inverted image of A R at a r\\nA R situated beyond the principal focus. Lines drawn\\nfrom A and R through C.C. are secondary axes. Parallel\\nrays from A and R converge and cross at the principal\\nfocus (P.F.).\\nWhere D P and F E intersect the secondary axes, the in-\\nverted image a r of A R is situated. When the object, as\\nin this instance, is situated beyond the center of curvature,\\nthe image is smaller than the object. As the image and\\nobject are conjugate to each other, they are interchange-\\nable, and in such a case the image would be larger than\\nthe object and inverted. This is always true when the\\nFig. 6.\\nobject is situated between the center of curvature and the\\nprincipal focus. When an object is situated at the center\\nof curvature, its image is equally distant and of the same\\nsize, but inverted.\\nTilting a concave mirror gives an object placed inside of\\nits principal focus the appearance of moving as the mirror\\nis tilted but if the object is situated beyond the principal\\nfocus, the object appears to move in the opposite direction.\\nReflection from a Convex Mirror. All rays are re-\\nflected divergently from a convex mirror, and parallel rays\\ndiverge as if they came from the principal focus situated\\nbehind the mirror at a distance equal to one-half its radius", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0024.jp2"}, "25": {"fulltext": "OPTICS.\\n17\\nof curvature. The principal focus of a convex mirror is\\ntherefore negative. The foci of convex mirrors are virtual.\\nImages Formed by a Convex Mirror. These are\\nalways virtual, erect, and smaller than the object. The\\ncloser the object, the larger the image and the more distant\\nthe object, the smaller the image. Tilting a convex mirror,\\nthe image does not appear to change position.\\nIn figure 7 parallel rays from the object A R are reflected\\nfrom the mirror as if they came from the principal focus situ-\\nated at one-half the distance of the center of curvature, C.C.\\nLines drawn from the extremes of the object to C.C. are\\nA\\nL _-\u00e2\u0080\u0094\\nr^\\n-_-_.\\nP.F.\\nU--\\nJ\\nF\\nFig. 7.\\nsecondary axes, and the image is situated at the point of\\nintersection of the secondary axes and the rays from the\\nprincipal focus and as these meet behind the mirror, the\\nimage is virtual and erect.\\nRefraction. From the Latin r ef ranger e, meaning to\\nbend back i. e., to deviate from a straight course. Refrac-\\ntion may be defined as the deviation w r hich takes place in\\nthe direction of rays of light as they pass from one medium\\ninto another of different density.*\\nAs ordinarily understood in ophthalmology, refraction has come to mean\\nthe optic condition of an eye in a state of repose or under the physiologic effect\\nof a cycloplegic.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0025.jp2"}, "26": {"fulltext": "i8\\nREFRACTION AND HOW TO REFRACT.\\nTwo laws govern the refraction of rays of light\\n1. A ray of light passing from a rare into a denser\\nmedium is deviated or refracted toward the perpendicular.\\n2. A ray of light passing from a dense into a rarer\\nmedium is deviated or refracted away from the perpen-\\ndicular.\\nAside from these laws, there are other facts in regard\\nto rays of light that should have consideration. A ray\\nof light will continue its straight course through any\\nnumber of different transparent media, no matter what their\\ndensities, so long as it forms right angles with the surface\\nICE\\nFLINT GLASS\\nCROWN\\nPLATE\\nFig. 8.\\nP IG. 9.\\nor surfaces. Such a ray is spoken of as the normal or\\nperpendicular such surfaces are plane, the surfaces and\\nperpendicular forming right angles. (See Fig. 8.) In any\\ncase of refraction the incident and refracted rays may be\\nsupposed to change places.\\nFigure 9 shows the perpendicular (P P) to a piece of\\nplate glass with plane surfaces. The ray in air incident at\\nO on the surface S F is bent in the glass toward the per-\\npendicular, P P. The dotted line shows the direction the\\nray would have taken had it not been refracted. As the\\nray in the glass comes to the second surface at R, and", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0026.jp2"}, "27": {"fulltext": "OPTICS. 19\\npasses into a rarer medium, it is deviated from the perpen-\\ndicular, P P. The ray now continues its original direction,\\nbut has been deviated from its course it has undergone\\nlateral displacement.\\nCritical Angle or Limiting Angle of Refraction. This\\nis the angle of incidence which just permits a ray of light\\nin a dense medium to pass out into a rare medium. The\\nsize of the critical angle depends upon the index of refrac-\\ntion of different substances. Figure 10 shows an electric\\nlight suspended in water. The ray from this light which\\nforms an angle of 48 35 with the surface of the water\\nFig. 10. Critical Angle.\\nwill be refracted and pass out of the water, grazing its sur-\\nface but those rays which form an angle greater than\\n48 35 will not pass out of the water, but will be reflected\\nback into it. The surface separating the two media be-\\ncomes a reflecting surface and acts as a plane mirror.\\nThe critical angle for crown glass is 40 49/.\\nIndex of Refraction. By this is meant the relative\\ndensity of a substance or the comparative length of time\\nrequired for light to travel a definite distance in different\\nsubstances. The absolute index of refraction is the\\ndensity or refractive power of any substance as compared", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0027.jp2"}, "28": {"fulltext": "20\\nREFRACTION AND HOW TO REFRACT.\\nwith a vacuum. According to the first law of refraction, a\\nray of light passing from a rare into a dense medium is\\nrefracted toward the perpendicular in other words, the\\nangle of refraction is smaller, under these circumstances,\\nthan the angle of incidence. In the study of the compara-\\ntive density of any substance it\\nwill be seen that the angle of re-\\nfraction is usually smaller the\\nmore dense the substance this\\nis well illustrated in figures 1 1\\nand 12.\\nThe greater the density, the\\nslower the velocity or the more\\neffort apparently for the wave or ray to pass through\\nthe substance. This is illustrated in figure 13, where a\\nray or wave of light is seen passing at right angles through\\ndifferent media. A ray passes through a vacuum without\\napparent resistance, but in its course through air it is\\nslightly impeded, so that air has an index of refraction of\\n1\\nr\\n3\\nA\\nJ\\nFig. 11.\\nFig. 12.\\nI\\nIce\\nGlass\\nDiamond\\nVacuum\\nAir\\nFig. 13.\\n1.00029 -f- when compared with a vacuum but as this is so\\nslight, air and a vacuum are considered as one for all pur-\\nposes in refraction. To find the index of refraction of any\\nsubstance as compared with a vacuum or air, it is neces-\\nsary to divide the sine of the angle of incidence by the sine\\nof the anoje of refraction.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0028.jp2"}, "29": {"fulltext": "OPTICS.\\n21\\nIn figure 14 the angle of incidence P C I is the angle\\nformed by the incident ray I with the perpendicular, P P.\\nThe angle of refraction P C R is the angle formed by the\\nrefracted ray with the perpendicular, P P. Drawing the\\ncircle P H P O around the point of incidence C, and then\\ndrawing the sines D\\nX and B F, perpen-\\ndiculars to the per-\\npendicular P P, divide\\nthe sine D X of the\\nangle of incidence by\\nthe sine F B of the\\nangle of refraction to\\nobtain the index of\\nrefraction in this in-\\nstance, water as com-\\npared with air. D X\\nequaling 4 and F B\\nequaling 3, then 4 di-\\nvided by 3 will equal or\\n1.33 -f, the index of refraction of water as compared with air.\\nTo find the index of refraction of a rare as compared\\nwith a dense substance, divide the sine of the angle of\\nrefraction by the sine of the angle of incidence i. e., air\\nas compared with water would be or 0.75.\\np\\nAir\\nC\\nWater\\n3 2 iV/\\n_J^\\\\B\\np\\nFig. 14.\\nIndexes of Refraction.\\nAir, 1.00029\\nWater, 1. 333\\nCornea, 1-3333\\nCrown glass, 1. 5\\nFlint glass, 1.58\\nCrystalline lens, nucleus, 1.43\\nintermediate layer, 1.41\\ncortical layer, 1.39", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0029.jp2"}, "30": {"fulltext": "22\\nREFRACTION AND HOW TO REFRACT.\\nA prism is any refracting substance bounded by plane\\nsurfaces which intersect each other. The sides of a prism\\nare the inclined surfaces. The apex is where the two plane\\nsurfaces meet. The base of the prism is the thickest part\\nof the prism. The refracting angle is the angle at which\\nthe sides come together.\\nPosition of a Prism. When a prism is placed in front\\nof an eye, its position is indicated or described by the direc-\\ntion in which its base is situated base down means that the\\nthick part of the prism is toward the cheek base up means\\nthat the thick part of the prism is toward the brow base\\nin means that the thick part of the prism is toward the\\nFig. 15.\\nFig. 16.\\nnose and base out means that the thick part of the prism\\nis toward the temple.\\nPrismatic Action. Rays of light passing through a\\nprism are always refracted toward the base of the prism.\\nIf an incident ray is perpendicular to the surface of a prism,\\nthere will be only one refraction, and that takes place at\\nthe point of emergence. The angle of incidence in this\\ninstance will equal the angle of the prism, and the maximum\\ndeviation takes place, as all the refraction is done at one\\nsurface.\\nIn figure 1 5 the incident ray (I) is perpendicular to the\\nsurface A B, and is not refracted until it comes to the sur-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0030.jp2"}, "31": {"fulltext": "OPTICS. 23\\nface A C at E, when it is bent toward the base B C, all the\\nrefraction taking place at the surface A C.\\nIf an incident ray forms an angle other than a right\\nangle with the first surface of the prism, then it will be re-\\nfracted twice as it enters and as it leaves the prism.\\nIn figure 16 X N is the perpendicular to the surface A B.\\nThe ray (I) incident at N is refracted toward this perpen-\\ndicular and follows the course N E inside of the prism.\\nOn emergence it is refracted from the perpendicular E P of\\nthe surface A C, and in the direction of the base of the prism.\\nIf the incident ray (I) so falls upon the surface A B that\\nthe refracted ray (N E) is parallel to the base (B C), and\\nthe emergent ray is such that the angle of emergence\\nequals the angle of incidence (I N X), as in this instance, then\\nthe angles of incidence and of emer-\\ngence are equal, and the deviation is\\nat a minimum, or the least possible.\\nAngle of Deviation (Fig. 17).\\nThis is the angle formed between\\nthe directions of the incident and\\nemergent rays, and measures the total\\ndeviation. In all prisms of ten degrees\\nor less the angle of deviation is equal\\nto half the angle of the prism, but in prisms of more than\\nten degrees the angle of deviation increases.\\nSummary. Prisms do not cause rays of light to con-\\nverge or to diverge rays that are parallel before refraction\\nare parallel after refraction. Therefore, prisms do not form\\nimages prisms have no foci.\\nEffect of a Prism. An object viewed through a prism\\nhas the appearance of being displaced, and in a direction\\nopposite to the base i. e., toward the apex.\\nRays from the object (X, Fig. 18) strike the prism at C,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0031.jp2"}, "32": {"fulltext": "2 4\\nREFRACTION AND HOW TO REFRACT.\\nundergo double refraction, and, falling upon the retina of the\\neye, are projected back in the direction in which they\\nwere received, and the apparent position of X is changed\\nto X away from the base of the\\nprism and tozvard the apex.\\nNumbering of Prisms. Form-\\nerly, prisms were numbered by their\\nrefracting angles now, however,\\ntwo other methods are in use\\nDennett s method, known as the\\ncentrad and Prentice s method,\\nknown as the prism-diopter.\\nDennett s Method (Fig. 19). The unit, or centrad (ab-\\nbreviated V is a prism that will deviate a ray of light the\\nY^-q part of the arc of the radian. This is calculated as\\nfollows As much of the circumference of a circle is taken\\nas will equal the length of its radius of curvature this is\\ncalled the arc of the radian, and equals 57.295 degrees.\\nThe arc of the radian is then divided into 100 parts. A\\nFig. 1\\nprism, base down, at the center of curvature that will devi-\\nate a ray of light downward just y^- part of the arc of the\\nradian is a one centrad, and equals y-i-g- of 57.295 degrees,\\nor 0.57295 of a degree.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0032.jp2"}, "33": {"fulltext": "OPTICS.\\n25\\nTen centrads will deviate a ray of light ten times as\\nmuch as one centrad, or 10 X 0.57295 5.7295 degrees,\\netc.\\nPrentice s Method (Fig. 20). The unit, or prism-diopter\\n(abbreviated P.D., or A), is a prism\\nthat will deviate a ray of light 98765432 10\\njust I cm. for each meter of dis-\\ntance that is, the y^-g- part of\\nthe radius measured on the tan-\\ngent. The deviation always be-\\ning 1 cm. for each meter of dis-\\ntance, 1 P. D. will deviate a ray of\\nlight 2 cm. for 2 meters of dis-\\ntance 3 cm. for 3 meters, etc.\\nThe comparative values of cen-\\ntrads and prism-diopters is quite\\nuniform up to 20, but above 20 9876543210\\nthe centrad is the stronger.\\nNeutralization of Prisms.\\nKnowing that rays of light are de-\\nviated by centrads and prism-\\ndiopters up to 20, in the ratio of\\n1 cm. for each meter of distance,\\nthen to find the numeric strength\\nof any prism all that is necessary\\nis to hold the prism over a series\\nof numbered parallel lines, sepa-\\nrated by an interval of I cm. or\\nfraction thereof, and note the\\namount of displacement. For example, figure 2 1 shows a\\nseries of vertical lines of a cm. apart, and numbered from\\no to 9 an X is placed at the foot of the o line. Holding a\\nprism, base to the right, at a distance of of a meter (as\\n3\\nFig. 2]", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0033.jp2"}, "34": {"fulltext": "26\\nREFRACTION AND HOW TO REFRACT.\\nthe lines are y^ of a cm. apart) and looking through the prism\\nat the X on the o line, it will be seen that the X has been\\ndisplaced to the line to the left corresponding to the number\\nof centrads or prism-diopters in the prism in this instance\\nthree.\\nTable Showing the Equivalence of Centrads in Prism-diopters\\nand in Degrees of the Refracting Angle (Index of\\nRefraction 1.54).\\nCentr\\nads. Prism-diopters.\\nRefracting Angle.\\nj\\nI.\\ni\u00c2\u00b0.oo\\n2\\n2.000I\\n2\u00c2\u00b0. 12\\n3\\n3.0013\\n3 \u00c2\u00b0.i8\\n4\\n4.0028\\n4 23\\n5\\n5-0045\\n5\u00c2\u00b0- 28\\n6\\n6.0063\\n6\u00c2\u00b0. 32\\n7\\n7.0115\\n7\u00c2\u00b0-35\\n8\\n8.0172\\n8\u00c2\u00b0. 3 8\\n9\\n9.0244\\n9\u00c2\u00b0-39\\n10\\nIO.033\\nio\u00c2\u00b0.39\\n11\\nII.044\\n37\\n12\\n12.057\\n12 34\\n13\\nI3-074\\ni3\u00c2\u00b0-29\\n14\\n14.092\\nl 4 \u00c2\u00b0.23\\n15\\n15.114\\n150.16\\n16\\n16.138\\ni6\u00c2\u00b0.o8\\n17\\n17.164\\ni6\u00c2\u00b0. 9 8\\n18\\n18.196\\ni7\u00c2\u00b0-85\\n19\\n19.230\\ni8\u00c2\u00b0.68\\n20\\n20.270\\ni9\u00c2\u00b0-45\\n25\\n25-55\\n23\u00c2\u00b0-43\\n30\\n30.934\\n26\u00c2\u00b0.8i\\n35\\n36.50\\n29\u00c2\u00b0.72\\n40\\n42.28\\n32\u00c2\u00b0. 18\\n45\\n48.30\\n34 20\\n50\\n54-514\\n35\u00c2\u00b0-94\\n60\\n68.43\\n38\u00c2\u00b0-3i\\n70\\n84.22\\n39\u00c2\u00b0-73\\n80\\n102.96\\n40\u00c2\u00b0.29\\n90\\n126.01\\n40\u00c2\u00b0.49\\n100\\n155-75\\n39\u00c2\u00b0- 14\\nOr a prism may be neutralized by placing another prism\\nin apposition to it, with their bases opposite, so that in look-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0034.jp2"}, "35": {"fulltext": "OPTICS. 27\\ning through the two prisms at a straight line, no matter at\\nwhat distance, the straight line will continue to make one\\nstraight line through the prisms the strength of the neu-\\ntralizing prism will equal the strength of the prism being\\nneutralized.\\nUses of Prisms. 1. To detect malingerers who profess\\nmonocular blindness so as to obtain damages for supposed\\ninjuries, or who wish to escape war service, or those cases\\nof hysteric blindness wishing to create sympathy. This\\ntest or use of a prism is known as the diplopia test, and is\\npractised as follows A seven P. D., base up or down, with\\na blank are placed in the trial-frame corresponding to the\\nblind eye nothing is placed in front of the seeing eye\\nthe trial-frame, thus armed (without the patient seeing what\\nis being done), is placed on the patient s face and he is in-\\nstructed to read the card of test-letters on the wall across\\nthe room. While he is thus busy reading, and purposely\\ncontradicted by the surgeon, so as to get his mind from his\\ncondition, the surgeon suddenly removes the blank from\\nthe blind eye. The patient exclaiming that he sees two\\ncards and two of all the letters proves the deception.\\n2. Occasionally, to counteract the effects of strabismus,\\nor diplopia due to a paralysis of one or more of the extra-\\nocular muscles. For example A patient looking at a\\npoint of light focused on the macula (M) of the left eye\\n(L), the right eye being turned in toward the nose, receives\\nthe rays upon the retina to the nasal side of the macula,\\nand hence projects the rays outward to the right, giving a\\nfalse image to the right side a prism of sufficient strength\\nis then placed with its base toward the temple (base out)\\nover the right eye, so that the rays from the light may fall\\nupon the macula (M), and the diplopia will be corrected.\\n(See Fig. 22.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0035.jp2"}, "36": {"fulltext": "28\\nREFRACTION AND HOW TO REFRACT.\\n3. To test the strength of the extra-ocular muscles A\\npatient looking with both eyes at a distant point of light\\nis made to see one light just above another by placing a\\n3 P. D., base down or up, before either eye, and if a 2^\\nP. D. did not produce diplopia when similarly placed, the\\nstrength of his vertical recti is then represented by 2^\\nP. D. The strength of the prism placed base in which,\\nFig. 22.\\nif increased, would produce diplopia is the strength of the\\nexterni and the strength of the prism or prisms placed\\nbase outward which, if increased, would produce diplopia\\nis the strength of the interni.\\n4. For exercise of weak muscles. (See p. 185.)\\nLenses. A lens is a portion of transparent substance\\n(usually of glass) having one or both surfaces curved.\\nThere are two kinds of lenses spheric and cylindric.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0036.jp2"}, "37": {"fulltext": "OPTICS. 29\\nSpheric Lenses. Abbreviated S. or sph. Spheric\\nlenses are so named because their curved surfaces are sec-\\ntions of spheres. A spheric lens is one which refracts\\nrays of light equally in all meridians or planes. Spheric\\nlenses are of two kinds convex and concave.\\nA convex spheric lens is thick at the center and thin\\nat the edge, (Figs. 23, 24, 25.) The following are synony-\\nmous terms for a convex lens (1) Plus (2) positive (3)\\ncollective (4) magnifying. A convex lens is denoted by\\nthe sign of plus\\nVarieties or Kinds of Convex Lenses.\\n1. Planoconvex, meaning one surface flat and the other\\nconvex. It is a section of a\\nsphere. (See Fig. 23.)\\n2. Biconvex, also called con-\\nvexoconvex or bispheric, for the\\nreason that it is equal to two\\nplanoconvex lenses with their\\nplane surfaces together. (Fig.\\n2 4-) Fig. 23. Fig. 24. Fig. 25.\\n3. Concavoconvex. This lens\\nhas one surface concave and the other convex, the convex\\nsurface having the shortest radius of curvature. (Fig. 25.)\\nThe following are synonymous terms for a concavocon-\\nvex lens (1) Periscopic (2) convex meniscus (3) con-\\nverging meniscus (meniscus meaning a small moon). (See\\nFig. 25.) A periscopic lens enlarges the field of vision,\\nand is of especial service in presbyopia.\\nA Concave Spheric Lens. Such a lens is thick at the\\nedge and thin at the center. (Figs. 26, 27, 28.) The fol-\\nlowing are synonymous terms for a concave lens (1) Minus\\n(2) negative (3) dispersive (4) minifying. A concave lens\\nis denoted by the sign of minus", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0037.jp2"}, "38": {"fulltext": "3o\\nREFRACTION AND HOW TO REFRACT.\\nVarieties or Kinds of Concave Lenses.\\n1. Planoconcave, meaning one surface flat and the other\\nconcave. (Fig. 26.)\\n2. Biconcave, also called concavoconcave or biconcave\\nspheric, for the reason that it is\\nequal to two planoconcave lenses\\nwith their plane surfaces to-\\ngether. (Fig. 27.)\\n3. Convexoconcave. This lens\\nhas one surface convex and the\\nother concave, the concave sur-\\nFig. 26. Fig. 27. Fig. 28. face having the shortest radius\\nof curvature. (Fig. 28.) The\\nfollowing are synonymous terms for a concavoconvex lens\\n(1) Concave meniscus (2) diverging meniscus (3) peri-\\nscopic.\\n7\\ni\\n(7\\ni\\nFig. 29.\\nFig. 30.\\nA spheric lens may be considered as made up of a series\\nof prisms which gradually increase in strength from the\\ncenter to the periphery, no matter whether the lens be con-\\ncave or convex.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0038.jp2"}, "39": {"fulltext": "OPTICS. 3 1\\nIn the convex sphere the bases of the prisms are toward\\nthe center of the lens, whereas in the concave the bases of\\nthe prisms are toward the edge. (See Figs. 29, 30.)\\nKnowing that a prism refracts rays of light toward its\\nbase, it may be stated as a rule that every lens bends rays\\nof light more sharply as the periphery is approached i. e.,\\nat the periphery the strongest prismatic effect takes place.\\nLens Action. As a ray of light will travel in a straight\\nline so long as it continues to form right angles with sur-\\nfaces, then the ray A in figure 3 1 passes through the bicon-\\nvex lens unrefracted, or without any deviation from its\\ncourse whatsoever, for at its points of entrance and emer-\\nFig. 31.\\ngence the surfaces of the lens are plane to each other. This\\nray is called the axial ray, and the line joining the centers\\nof curvature of the two surfaces is called the principal axis.\\nThe axis of a planoconvex or planoconcave lens is the line\\ndrawn through the center of curvature perpendicular to the\\nplane surface.\\nThe ray B in figure 31, though parallel to the ray A,\\nforms a small angle of incidence, and must, therefore, be\\nrefracted toward the perpendicular to the surfaces of the\\nlens, and, passing through the lens, will meet the axial ray\\nat P.F. The rays C, D, and E, also parallel to A and B,\\nform progressively larger angles with the surface of the lens,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0039.jp2"}, "40": {"fulltext": "32 REFRACTION AND HOW TO REFRACT.\\nand finally meet the axial ray at P.F. It will be seen at\\nonce that the rays all meet at P.F., showing the progres-\\nsively stronger prismatic action that takes place as the per-\\niphery of the lens is approached.\\nIn figure 32 we have similar rays, A, B, C, D, and E,\\npassing through a con-\\ncave lens. The axial ray\\nA passes through the cen-\\nters of curvature unre-\\nfracted, but the rays B,\\nC, D, and E are progres-\\nsively refracted more and\\nmore as the periphery is\\napproached. The ray E\\nin each instance is refracted the most.\\nThe action of a convex lens is similar to that of a concave\\nmirror and the action of a concave lens is similar to that of\\na convex mirror.\\nPrincipal Focus. The principal focus of a lens may be\\ndefined (1) as the point where parallel rays, after refrac-\\ntion, come together on the axial ray or (2) as the shortest\\nfocus or (3) as the focal point for parallel rays.\\nFocal Length. This is the distance measured from the\\noptic center to the principal focus. The principal focus\\nof an equally biconvex or biconcave lens of crown glass is\\nsituated at about the center of curvature for either surface\\nof the lens. A lens has two principal foci, an anterior and\\na posterior, according to the direction from which the par-\\nallel rays come, or as to which radius of curvature is re-\\nferred to. (See p. 59.) Figure 3 1 shows parallel rays, B,\\nC, D, and E, passing through a convex lense and coming\\nto a focus on the axial ray (A) at P. F. and as the path of\\na ray passing from one point to another is the same, no", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0040.jp2"}, "41": {"fulltext": "optics. 3 3\\nmatter what its direction, then if a point of light be placed\\nat the principal focus of a lens, its rays will be parallel after\\npassing back through the lens. This is equivalent to what\\ntakes place in the standard or emmetropic eye. An eye, in\\nother words, which has its fovea situated just at the princi-\\npal focus of its dioptric media, such an eye in a state of rest\\nreceives parallel rays exactly at a focus upon its fovea, and\\ntherefore is in a condition to project parallel rays outward.\\nConjugate Foci. Conjugate meaning yoked to-\\ngether. The point from which rays of light diverge\\n(called the radiant) and the point to which they converge\\n(called the focus) are conjugate foci or points. For in-\\nstance, in figure 33 the rays diverging from A and passing\\nFig. 33.\\nthrough the lens converge to the point B then the points\\nA and B are conjugate foci. They are interchangeable, for\\nif rays diverged from B, they would follow the same path\\nback again and meet at A. The path of the ray C C is\\nthe same whether it passes from A to B or from B to A\\nthere is no difference. It is by the affinity of these points\\nfor each other, with respect to their positions, that they are\\ncalled conjugate.\\nThe conjugate foci are equal when the point of diver-\\ngence is at twice the distance of the principal focus. The\\nequivalent to conjugate foci is found in the long or myopic\\neye an eye, in other words, which has its fovea situated\\nfurther back than the principal focus of its dioptric media,\\nthe result being that rays of light from the fovea of such an", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0041.jp2"}, "42": {"fulltext": "34 REFRACTION AND HOW TO REFRACT.\\neye would be projected convergently after passing out of\\nthe eye, and would meet at some point inside of infinity.\\nIn other words, only rays which have diverged from some\\npoint inside of six meters will focus upon the fovea of this\\nlong eye. The fovea of the myopic eye represents a con-\\njugate focus. A myopic eye is in a condition to receive\\ndivergent rays of light at a focus on its retina and to emit\\nconvergent rays.\\nOrdinary Foci. When rays of light diverge from some\\npoint inside of infinity (six meters) they will be brought to\\na focus at some point on the other side of a convex lens,\\nbeyond its principal focus this point is called an ordinary\\nfocus. A lens may have many foci, but only two principal\\nFig. 34.\\nfoci. The further away from a lens the divergent rays pro-\\nceed, the nearer to the principal focus on the other side of\\nthe lens will they converge. As the divergent rays are\\nbrought closer to the lens they reach a point where they\\nwill not focus, but will pass parallel after refraction. This\\npoint is the principal focus. (See Fig. 34.) A lens, there-\\nfore, has as many foci as there are imaginary points on the\\naxial ray between the principal focus and infinity.\\nWhen rays of light diverge from some point closer to a\\nlens than its principal focus, they do not converge, but,\\nafter refraction, continue divergently their focus now is\\nnegative or virtual, and is found by projecting these diver-\\ngent rays back upon themselves to a point on the same", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0042.jp2"}, "43": {"fulltext": "OPTICS.\\n35\\n(See\\nside of the lens from which they appeared to come.\\nFig- 35-)\\nThis is the equivalent of what takes place in a short or\\nhyperopic eye, an eye which has its macula closer to its\\ndioptric media than its principal focus. In a state of rest\\n-\u00c2\u00a3,F.\\nFig. 35.\\nthe fovea of such an eye would project outward divergent\\nrays, and would only be in a position to receive convergent\\nrays of light at a focus upon its fovea.\\nSecondary Axes. In the study of the direction of a ray\\nof light passing through a dense medium with plane sur-\\nFig. 36.\\nfaces, it was found that it underwent lateral displacement\\n(see Fig. 9), and so in lenses there is a place where rays\\nundergo lateral displacement. Figure 36 shows a convex\\nlens of considerable thickness, and on each side is drawn a\\nradius of curvature (C C). The ray indicated by the arrow", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0043.jp2"}, "44": {"fulltext": "36\\nREFRACTION AND HOW TO REFRACT.\\npassed through the two surfaces, has undergone lateral\\ndisplacement, but continues in its original direction such\\nrays are called secondary rays or axes. The incident ray\\nis projected toward N 1 in the lens on the axial ray, and\\nthe emergent ray, if projected backward, would meet the\\naxial ray at N 2 These points on the axial ray are such\\nthat a ray directed to one before refraction, is directed to\\nthe other after refraction. The points N 1 and N 2 are\\nspoken of as nodal points. Every lens, therefore, has two\\nnodal points, but in thin lenses the deviation of the second-\\nary rays is so slight that, for all practical purposes, only\\nFig. 37.\\none nodal point is recognized. It is spoken of as the\\noptic center.\\nOptic Center. This term is used synonymously with\\nnodal point, and is the point where the secondary rays (s.a.\\nin Fig. 37) cross the axial ray. It is not always the geo-\\nmetric center. Rays of light crossing the optic center in thin\\nlenses are not considered as undergoing refraction. (See\\nFig. 37-)\\nAction of Concave Lenses. Rays of light passing\\nthrough a concave lens, no matter from what distance, are\\nalways refracted divergently, and its focus is, therefore,\\nalways negative or virtual, and is found by projecting these", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0044.jp2"}, "45": {"fulltext": "OPTICS.\\n37\\ndivergent rays backward in the direction from which they\\nappear to come until they meet at a point on the axial ray.\\nThe principal focus and conjugate foci of concave lenses\\nare found in the same way as in convex lenses. (See Figs.\\n32, 40.)\\nImages Formed by Lenses. An image formed by a\\nlens is composed of foci, each one of which corresponds\\nto a point in the object. Images are of two kinds real and\\nvirtual.\\nA Real Image. This is an image formed by the actual\\nmeeting of rays such images can always be projected on\\nto a screen.\\nA Virtual Image. This is one that is formed by the\\nprolongation backward of rays of light to a point.\\nFig. 38.\\nTo find the position and size of an image it is necessary\\nto obtain the conjugate foci of the extremes of the object,\\nas the image of an object is equal to the sum of its inter-\\nmediate points. Only two rays are required for this pur-\\npose, one parallel to the axial ray, and one secondary ray\\npassing through the optic center the image of the extreme\\npoint of the object will be located at the point of inter-\\nsection of these rays. In figure 38 A B is an object in\\nfront of a convex lens, o is the optic center and P. F.\\nthe principal focus. A ray drawn from A parallel to the\\naxial ray o, and a secondary ray from the same point drawn", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0045.jp2"}, "46": {"fulltext": "38 REFRACTION AND HOW TO REFRACT.\\nthrough the optic center, will give at their point of inter-\\nsection the conjugate focus of the luminous point A, which\\nwill be at A In the same way the conjugate focus of B\\nand points intermediate in the object may be obtained. A\\nB is a real inverted image of A B the size of the image\\n.of A B depends upon the distance of the object from\\nthe lens. The relative sizes of image and object are as\\ntheir respective distances from the optic center of the lens.\\nFor example, if an object ten millimeters high is three\\nmeters (3000 mm.) from the optic center of a lens, and its\\nimage is sixty millimeters from the lens,- the image will be\\nTSTo or To \u00c2\u00b0f the s i ze \u00c2\u00b0f the object that is, the image will\\nbe ^-g- of ten millimeters (the height of the object) namely,\\nj^ of a millimeter high.\\nAs conjugate foci are interchangeable, then in figure 38\\nif A W was the object, the image A B would be the image\\nof A W and, therefore, larger than the object.\\nThree facts should be borne in mind in the study of real\\nimages formed by a convex lens\\n1. The object and image are interchangeable.\\n2. The object and the real image are on opposite sides Qf\\nthe lens, and,\\n3. As the rays which pass through the optic center\\ncross each other at this point, the real image must be in-\\nverted.\\nRays of light from an object situated at the distance of\\nthe principal focus would proceed parallel after refraction,\\nand no image of the object would be obtained.\\nIf an object is situated just beyond the principal focus,\\nthen the image would be larger than the object, real and\\ninverted. (See Fig. 38^ reversing image for object.)\\nIf an object is situated at twice the distance of the prin-\\ncipal focus, then its image would be of the same size, real,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0046.jp2"}, "47": {"fulltext": "OPTICS.\\n39\\ninverted, and at a corresponding distance, as these conju-\\ngate foci are equal.\\nIf an object is situated at a greater distance than twice\\nthe principal focus, and nearer than infinity, its image will\\nbe real, inverted, and smaller than the object.\\nFig. 39.\\nRays of light from an object situated closer to a lens\\nthan its principal focus would be divergent after refraction,\\nand could only meet by being projected backward the\\nimage would, therefore, be larger than the object, erect, and\\nFig. 40.\\nvirtual. Such an image is only seen by looking through\\nthe lens the lens in this instance being a magnifying\\nglass. (Fig. 39.)\\nImages Formed by Concave Lenses. These images are\\nalways erect, virtual, and smaller than the object. (See\\nFig. 40.) A concave lens is, therefore, a minifying lens.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0047.jp2"}, "48": {"fulltext": "40 REFRACTION AND HOW TO REFRACT.\\nParallel rays from the extremes of the object A R form the\\ndivergent ray A r and R after refraction. Secondary rays\\npass through the optic center o unrefracted, A and R\\nAt the points of intersection where these rays meet after\\nbeing projected backward, the image of A R is found,\\nerect, virtual, and diminished in size. This image is only\\nseen by looking through the lens.\\nNumeration of Lenses. Formerly, lenses were num-\\nbered according to their radii of curvature in Paris inches\\n(27.07 mm.). The unit was a lens that focused parallel\\nrays of light at about the distance of one English inch\\n(25.4 mm.) from its optic center.\\nAs lenses for purposes of refraction were never as strong\\nas the unit, they were numbered by fractions, thus showing\\ntheir relative strength as compared to this unit for instance,\\na lens that was one-fourth the strength of the unit was\\nexpressed by the fraction or a lens that was one-\\nsixteenth the strength of the unit was expressed as etc.,\\nthe denominator of the fraction indicating the focal length\\nof the lens in Paris inches.\\nThere are three objections to this nomenclature (1)\\nThe difference in length of the inch in different countries\\n(2) the inconvenience of adding two or more lenses num-\\nbered in fractions with different denominators y^ Jg-\\n-f 4L- (3) the want of uniform intervals between num-\\nbers.\\nIn the new nomenclature, and the one that is now quite\\nuniversal, known as the metric or dioptric system (diopter,\\nabbreviated D.), a lens has been taken as the unit which\\nhas its principal focus at one meter distance (39.37 English\\ninches), commonly recognized as 40 inches.\\nLenses in the dioptric system are numbered according\\nto their refractive power and not according to their radii of", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0048.jp2"}, "49": {"fulltext": "OPTICS. 41\\ncurvature. The strength or refractive power of a dioptric\\nlens is, therefore, the inverse of its focal distance. To find\\nthe focal distance of any dioptric lens in inches or centi-\\nmeters, the number of diopters expressed must be divided\\ninto the unit of 40 inches or 100 cm. For example, a\\n2 D. lens has a focal distance of 40 -f- 2 equals 20 inches\\nor 100 cm. 2 equals 50 cm. A 4 D. has a focal dis-\\ntance of 40 -J- 4, equaling 10 inches, or 100 -f- 4, equaling 25\\ncm. Lenses that have a refractive power less than the unit\\nare not expressed in the form of fractions, but in the form of\\ndecimals for example, a lens which is only one-fourth, one-\\nhalf, or three-fourths the strength of the unit is written 0.25,\\n0.50, 0.75, respectively, and their focal distances are found\\nin the same way as in dealing with units 0.25 D. has a\\nfocal distance of 40 -f- 0.25 or 100-^-0.25, equaling 160\\ninches or 400 cm. 0.50 D. has a focal length of 40 -2-\\nO.50 or 100 -r- 0.50, equaling 80 inches or 200 cm. 0.75\\nD. has a focal length of 40 -f- 0.75 or 100 -5- 0.75\\nequaling 53 inches or 133 cm. Unfortunately, 0.25 D.,\\n0.50 D., and 0.75 D. are frequently spoken of as twenty-\\nfive, fifty, and seventy-five, which occasionally leads to\\nconfusion in the consideration of the strength and focal dis-\\ntance. The student should learn as soon as possible to\\nchange the old nomenclature into the new, as he will have\\nto make these changes in reading other text-books.\\nTo change the old focal length or inch system of\\nnumbering lenses into diopters, divide the unit (40 in.) by\\nthe denominator of the fraction, and the result will be an\\napproximation in diopters for example, equals j^\\nor 4 D. -fa equals or 2 D. The following table,\\nfrom Landolt, gives the equivalents in the old and new\\nsystems", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0049.jp2"}, "50": {"fulltext": "4 2\\nREFRACTION AND HOW TO REFRACT.\\nOLD SYSTEM.\\nNEW SYSTEM.\\nI.\\nII.\\nIII.\\nIV.\\nV.\\nVI.\\nVII.\\nVIII.\\nNo.\\nNo.\\nNo.\\nof the\\nFocal\\nFocal\\nof the\\nFocal\\nFocal\\nCorres-\\nLens,\\nDistance\\nDistance\\nEquiva-\\nLens,\\nDistance\\nDistance\\nponding\\nOld\\nin English\\nin Milli-\\nlent in\\nNew\\nin Milli-\\nin English\\nof the Old\\nSystem.\\nInches.\\nmeters.\\nDiopters.\\nSystem.\\nmeters.\\nInches.\\nSystem.\\n72\\n67.9\\n1724\\n0.58\\n0.25\\n4000\\n157 48\\n166.94\\n60\\n56.6\\n1437\\n0.695\\n0.5\\n2000\\n78 74\\n8346\\n48\\n45-3\\n1 150\\n0.87\\n0.75\\n1333\\n52.5\\n55 63\\n42\\n39-6\\n1005\\n0.99\\n1\\n1000\\n39 37\\n41-73\\n36\\n34\\n863\\n1. 16\\n\u00e2\u0096\u00a025\\n800\\n3i 5\\n33 39\\n30\\n28.3\\n718\\ni-39\\ni-5\\n666\\n26.22\\n27 79\\n24\\n22.6\\n574\\n1.74\\n*-75\\n57i\\n22.48\\n23-83\\n20\\n18.8\\n477\\n2.09\\n2\\n500\\n19.69\\n20.87\\n18\\n17\\n43 1\\n2.31\\n2.25\\n444\\n17.48\\n18-53\\n16\\n15\\n381\\n2.6\\n2.5\\n400\\n15-75\\n16.69\\n15\\n14. 1\\n358\\n2.79\\n3\\n333\\n13 7\\n13-9\\n14\\n13-2\\n335\\n2.98\\n3-5\\n286\\n11 26\\n11.94\\n13\\n12.2\\n312\\n3-20\\n4\\n250\\n9.84\\n10.43\\n12\\n11. 2\\n287\\n3-48\\n4-5\\n222\\n8.74\\n9 26\\n11\\n10.3\\n261\\n3-82\\n5\\n200\\n7.87\\n8-35\\n10\\n9-4\\n239\\n4.18\\n5-5\\n182\\n716\\n76\\n9\\n8-5\\n216\\n4-63\\n6\\n]66\\n6-54\\n6 93\\n8\\n7-5\\n190\\n5-25\\n7\\n143\\n563\\n5 97\\n7\\n6.6\\n167\\n5-96\\n8\\n125\\n4-92\\n5.22\\n6H\\n6.13\\n155\\n6.42\\n9\\n111\\n4-37\\n4-63\\n6\\n5-6\\n142\\n7.0\\n10\\n100\\n3-94\\n4 17\\n5^\\n52\\n132\\n7-57\\n11\\n9i\\n3.58\\n38\\n5\\n4-7\\n119\\n8.4\\n12\\n83\\n3-27\\n3-46\\nM\\n4.2\\n106\\n9-4\\n13\\n77\\n3-03\\n3.21\\n4\\n3-8\\n96\\n10.4\\nH\\n7i\\n2.8\\n2.96\\ns\u00c2\u00a3\\n3-3\\n84\\n11.9\\n15\\n67\\n2.64\\n2.8\\n3#\\n3-i\\n79\\n12.7\\n16\\n62\\n244\\n2-59\\n3\\n2.8\\n7i\\n14.0\\n17\\n59\\n2.32\\n2.46\\n2%\\n2.6\\n66\\nI5-I\\n18\\n55\\n2 17\\n2.29\\n2%\\n2.36\\n60\\n17.7\\n20\\n50\\n1.97\\n2.09\\nX\\n2.1\\n53\\n18.7\\n2\\n1.88\\n48\\n20.94\\nCylindric Lenses. Abbreviated cyl., c, or C. A cylin-\\ndric lens, usually called a cylinder, receives its name from\\nbeing a segment of a cylinder parallel to its axis. (See\\nFig. 41.) Occasionally cylinders are made with both sur-\\nfaces curved, and are then equivalent to two planocylinders\\nwith their plane surfaces together. A cylinder may be\\ndefined as a lens which refracts rays of light opposite to its\\nThis definition should be carefully borne in mind in\\naxis.\\ncontradistinction to a spheric lens, which refracts rays of\\nlight equally in all meridians. A cylindric lens has no one", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0050.jp2"}, "51": {"fulltext": "OPTICS.\\n43\\ncommon focus or focal point, but a line of foci, which is\\nparallel to its axis.\\nAxis of a Cylinder. That dimension of a cylindric lens\\nwhich is parallel to the axis of the original cylinder of\\nFig. 41,\\nFig. 42.\\nFig. 43.\\nwhich it is a part is spoken of as the axis, and is indicated\\non the lens of the trial-case by a short diamond scratch on\\nthe lens at its periphery, or by having a small portion of\\nFig. 44.\\nits surface corresponding to the axis ground at the edges,\\nor it may be marked in both ways. (See Fig. 43.) Cylin-\\nders are of two kinds convex and concave. (Figs. 41, 42.)\\nCylinder Action. A convex cylinder converges parallel", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0051.jp2"}, "52": {"fulltext": "44\\nREFRACTION AND HOW TO REFRACT.\\nF\\nFig. 45.\\nrays of light so that after refraction they are brought into\\na straight line which corresponds to the axis of the cylin-\\nder for instance, a 5 c yl- will converge parallel rays so\\nthat they come together in a straight line at the dis-\\ntance of eight inches,\\nor twenty centimeters,\\nand this straight line\\nwill be parallel to the\\naxis of the cylinder.\\n(Fig. 44.)\\nA concave cylin-\\nder diverges rays of\\nlight opposite to its\\naxis, as if they had diverged from a straight line on the\\nopposite side of the lens. (Fig. 45.)\\nSpherocy Under s. A spherocylinder is a combination\\nof a sphere and a cylinder, and is therefore a lens which has\\none surface ground with a spheric curve and the other sur-\\nface cylindric. A spherocylindric lens is also spoken of as\\nan astigmatic lens. (See Fig. 93.) A spherocylindric lens\\nis one which has two focal planes. Spherocylinders have\\ndifferent curves the spheric curve may be convex, with the\\ncylindric surface convex or the spheric surface may be\\nconcave, with the cylindric surface concave or the spheric\\nsurface may be convex, with the cylindric surface concave\\nor the spheric surface may be concave, with the cylindric\\nsurface convex.\\nThe Trial-Case (see Fig. 46). This case contains pairs\\nof plus and minus spheres and pairs of plus and minus\\ncylinders also prisms numbered from or y 2 to 20 A.\\nThe spheres are numbered in intervals of o. 1 2 up to 2 S.\\nand from 2 S. up to 5 S. the interval is 0.25 S.; and from\\n5 S. to 8 S. the interval is 0.50 S.; and from 8 S. to 22 S.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0052.jp2"}, "53": {"fulltext": "OPTICS.\\n45\\nthe interval is I S. The cylinders have similar intervals,\\nbut seldom go higher than 6 or 8 cyl.\\nThe trial-case also contains a trial -frame, which is used\\nto place lenses in. front of the patient s eyes. (See Fig. 47.)\\nThe eye -pieces of such a frame are numbered on the\\nperiphery in degrees of half a circle, so that the axis of a\\ncylinder can be seen during refraction. The left of the\\na 1\\nFig. 46.\\nhorizontal line in each eye-piece is recognized as the start-\\ning-place, or zero (o), and the degrees are marked from\\nleft to right on the lower half, counting around to the\\nhorizontal meridian, which at the right hand is numbered\\n1 80 this horizontal meridian is, therefore, spoken of as\\nhorizontal, zero (o), or 180 degrees. The meridian midway\\nbetween zero and 180 is spoken of as vertical, or 90 degrees.\\nIn some countries the meridians are differently num-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0053.jp2"}, "54": {"fulltext": "46\\nREFRACTION AND HOW TO REFRACT.\\nbered (see Fig. 48) for example, the vertical meridian is\\ncalled zero, and the degrees are marked on each side of\\nzero up to 90 degrees. Only the upper half of the eye -piece\\nis thus numbered, so that when a cylinder has the upper end\\nof its axis inclined toward the nose, the record would be so\\nmany degrees of inclination to the nasal side or if the upper\\nend of the cylinder was inclined toward the temple, the\\nrecord would be so many degrees to the temporal side.\\nFor example, in the right eye 15 degrees nasal would\\nFig. 47.\\nmean axis 75 on the ordinary trial-frame, and 15 degrees\\ntemporal would mean 105 degrees.\\nThe trial-case also contains other accessories, such as\\nblanks or blinders, a stenopeic slit, pin-hole disc, etc., all of\\nwhich are referred to in the text.\\nCombination of Lenses. The sign of combination\\nis\\nCombining Spheres. Any number of spheric lenses\\nplaced with their optic centers over each other, and sur-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0054.jp2"}, "55": {"fulltext": "OPTICS.\\n47\\nfaces together, will equal one lens the value of their sum\\nfor example, +2S. Q +1 S. Q +3 S. will equal -f 6 S.;\\nor a 2 S. 3 I S. 3 3 S. will equal a 6 S.\\nIf a plus and minus sphere, each of the same strength, be\\nplaced with their optic centers together, the refraction will\\nbe nothing, for the one will neutralize the effect of the other\\nfor instance, +4 S. and 4 S. will be equivalent to a piece\\nof plane glass, as the 4 S. will diverge rays of light as\\nmuch as the +4 S. will converge them, and the result\\nFig. 48.\\nis, rays of light parallel before refraction are parallel after\\npassing through such a combination. If, however, a plus\\nand a minus sphere of different strengths are placed together,\\nthe value of the resulting lens will equal their difference, in\\nfavor of the higher number; for instance, -f-4 S. and 2\\nS. will equal a -\\\\-2 S., the 2 S. neutralizing 2 S. of the\\n4S., leaving -f 2 S.\\nCombining Cylindric Lenses. Any number of cylin-\\ndric lenses placed together, with their axes in the same", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0055.jp2"}, "56": {"fulltext": "48 REFRACTION AND HOW TO REFRACT.\\nmeridian, are equal to a cylinder the value of their sum\\nfor example -f- 2 cyl. axis 90 degrees and -j- 3 cyl. axis 90\\ndegrees will equal a 5 cyl. axis 90 degrees or 2 cyl.\\naxis 1 80 degrees and 3 cyl. axis 1 80 degrees will equal\\na 5 cyl. axis 180 degrees or 2 cyl. axis 180 degrees\\nand +1 cyl. axis 180 degrees will equal a 1 cyl. axis\\n180 degrees.\\nAs a cylinder refracts rays of light only in the meridian\\nopposite to its axis, this opposite meridian can always be\\nfound by the following simple rule\\nAdd po when the given axis is 00 or less than po, and\\nsubtract po zvhen the given axis is more than po.\\nFor example 3 cyl. axis 90 refracts rays of light in\\nthe 180 degree meridian (90 -(-90= 180); or +3 cyl.\\naxis 75 refracts rays of light in the 165 meridian (75 90\\n165). A 3 cyl. axis 135 refracts rays of light in the\\n45 meridian (135 less 90 =45). A 2 cyl. axis 180 re-\\nfracts rays of light in the 90 meridian (180 less 90 90).\\nCombining two cylinders of the same strength and\\nsame denomination, with their axes at right angles to\\neach other, will equal a sphere of the same strength\\nand same denomination. For instance, +3 cyl. axis 90\\nand +3 c yl\u00c2\u00ab ax s 180, placed together, will equal a -f-3 S.\\ni. e. t the -j-3 cyl. at axis 90 will converge parallel rays in\\nthe 180 meridian, while the +3 cyl. axis 180 will converge\\nparallel rays in the 90 meridian, producing a principal\\nfocus therefore any sphere is also equal to two cylinders\\nof its same strength and same denomination with their\\naxes at right angles to each other.\\nCombining cylinders of different strength, but of the\\nsame denomination, with their axes at right angles to\\neach other, such a combination will equal a sphere and\\na cylinder of the same denomination. For example", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0056.jp2"}, "57": {"fulltext": "OPTICS.\\n49\\n-j-2 cyl. axis 75 O -f3 cyl. axis 165 will equal +2 S. C\\n1 cyl. axis 165. The -\\\\-2 cyl. axis 75 takes +2 of the\\n-f- 3 cyl. axis 165 and makes a +2 S., leaving -f- 1 cyl. axis\\nat 165 the result is then -f- 2 S. O 1 cyl. axis 165.\\nOr 3.50 cyl. axis 15 O 4.50 cyl. axis 105, will\\nequal 3.50 S. O 1 cyl. axis 105. The 3.50 axis 15\\ntakes 3.50 of the 4.50 and makes a 3.50 S.,\\nleaving 1 cyl. axis 165 this 1 cyl. axis 105 is now\\njoined to the 3.50 sphere, making 3.50 S. O I cyl.\\naxis 105.\\nCombining a sphere and a cylinder of the same\\nstrength, but of differ-\\nent denomination, will\\nequal a cylinder of the\\nopposite sign and opposite\\naxis from the cylinder\\ngiven. For example -f- 1\\nsphere O 1 cyl. axis 180\\nwill equal -f- 1 cyl. axis 90.\\nThe -f 1 S. equals two -f 1\\ncylinders, one at axis 90\\nand one at axis 180, and\\nthe 1 cyl. at axis 180 is\\nneutralized by the -f 1 cyl.\\nat the same axis, leaving\\nthe 1 cyl. axis 90. This may be better understood by the\\ndiagram (Fig. 49).\\nOr 3 S. O +3 cyl. axis 90 equals 3 cyl. axis 180.\\nThe 3 S. is equal to two 3 cylinders, one at axis 90\\nand one at axis 1 80 the one at axis 90 is neutralized by\\nthe +3 c yl- at the same axis, leaving 3 cyl. axis 180.\\nCombining a Sphere with a Weaker Cylinder of Dif-\\nferent Denomination. Such a combination should be\\n5\\n1.00\\nFig. 49.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0057.jp2"}, "58": {"fulltext": "5 3 REFRACTION AND HOW TO REFRACT.\\nchanged to its simplest form of expression, and will equal\\na sphere of the same denomination, of the value of their\\ndifference, combined with a cylinder of the same strength\\nas the cylinder given, but of opposite sign and axis. For\\nexample: +4 S. O 1 cyl. axis 180. The minus one\\ncylinder is refracting in the 90 degree meridian, therefore it\\nreduces the strength of the +4 S. in this axis, making it a\\nplus 3. The horizontal or 180 degree meridian of the plus\\n4 S. has not been altered, but still remains -f- 4, and the re-\\nsult is, plus 3 in the vertical meridian and plus 4 in the\\nhorizontal meridian, equaling, therefore, -f- 3 S. O ~f~ l\\ncyl. axis 90.\\nThe following rule will be of service in making this\\nchange, and, in fact, this rule will apply in any instance\\nwhere the sphere and cylinder are of different denomina-\\ntion, no matter what their respective strengths may be\\nRule. Subtract the less from the greater, and to the result\\nprefix the sign of the greater combine with this the same\\nstrength cylinder using the opposite sign and opposite axis.\\nExample +2.25 S. O 0.75 cyl. axis 75 degrees sub-\\ntracting the less from the greater 0.75 from +2.25), and\\nprefixing the sign of the greater will leave -f 1.50 S.\\nand combining with this the same strength cylinder (0.75),\\nwith opposite sign and axis (-f and 165), will be +0.75\\ncyl. axis 165. Result, +1.50 S. O +0.75 cyl. axis 165.\\nCombining a Sphere and Cylinder of the Same De-\\nnomination. This is recognized as the minimum or\\nsimplest form of expression, and is seldom changed. For\\nexample 2 S. O 6 cyl. axis 180 is considered as the\\nthinnest lens and the one with the least weight that can be\\nmade by such a combination. It may be changed, how-\\never, by the reverse of the rule above given, and will equal\\n8 S. O -f 6 cyl. axis 90.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0058.jp2"}, "59": {"fulltext": "OPTICS. 5 1\\nCombining Two Cylinders of Different Denominations\\nwith Opposite Axes. Commonly called cross cylinders.\\nSuch combinations can be written in three ways\\n1. -j-Cyl. 3 c yl. axes opposite.\\n2. -f Sphere 3 c yl\u00c2\u00ab (cylinder stronger than sphere).\\n3. Sphere -f-cyl. (cylinder stronger than sphere).\\nFor example 1.00 cyl. axis 180 -\\\\-2. 50 cyl. axis 90\\nmay be changed to one of the following\\n1. 00 s. 3 +3-5\u00c2\u00b0 cyl. ax i s 9\u00c2\u00b0 or\\n4-2.50 S. O 3-5\u00c2\u00b0 c yl- ax i s I ^o.\\nThe first formula shows that the vertical meridian must\\nalways be 1 and the horizontal or 180 meridian must\\nalways be +2.50, and with this clearly in mind, the second\\nand third formulas will be understood. In the second\\nformula 1. 00 S. O +3.50 cyl. axis 90) the +3- 50 cyl.\\nis only equal to +2.50, as it has 1 D. neutralized by 1\\nof the 1 sphere. In the third formula 2.50 S. O\\n3.50 cyl. axis 180) the 3.50 cylinder is only equal to\\n1. 00 cylinder, as it has 2.50 neutralized by +2.50 of\\nthe sphere.\\nIn any sphcrocylindric combination the meridian in which\\nthe axis of the cylinder lies has the strength of one lens, and\\nthe meridian opposite to the axis of the cylinder has the com-\\nbined values of sphere and cylinder i. e. y 1.00 S. O\\n3-5\u00c2\u00b0 c yl- ax i s 9\u00c2\u00b0 means 1.00 on the axis (90) of the\\ncylinder, and opposite to the axis therefore at 1 80, it equals\\n2.50 (\u00e2\u0080\u00941 and +3.50).\\nCross cylinders in themselves are seldom ordered in a\\nprescription, preference being given to a spherocylindric\\ncombination. When to order a plus sphere with a minus\\ncylinder, and when to order a minus sphere with a plus\\ncylinder, depends upon the individual lenses. For example", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0059.jp2"}, "60": {"fulltext": "52 REFRACTION AND HOW TO REFRACT.\\n0.50 cyl. axis 90 O 5.00 cyl. axis 180 equals +0.50\\nS. O 5.50 cyl. axis 180 or 5 S. O +5.50 cyl. axis 90.\\nPreference would be given to the plus sphere combina-\\ntion, on account of thinness and lesser weight of the lens.\\nThe following formula, 1 cyl. axis 180 degrees 3+3\\ncyl. axis 90 degrees, equals 1.00 S. +4 cyl. axis 90,\\nor +3 S. 3 4 cyl. axis 180, and for similar reasons\\npreference would be given to the minus sphere combination.\\nWhichever combination makes the thinnest and lightest\\nweight glass is the one to be ordered, as a rule.\\nThe student should practise these combinations at the\\ntrial-case, and be able at a glance to change one formula\\ninto another without diagram or rule.\\nPrescription Writing. In writing prescriptions for\\nlenses the right eye is indicated by one of three signs R,\\nRt, or O. D., the latter from the Latin for right eye,\\nOculus Dexter. The left eye is also indicated in one of\\nthree ways L, Lt, or O. S., the latter from the Latin\\nfor left eye, Oculus Sinister.\\nA prescription may call for any one of the following\\n-(-Sphere, written I4D. or -I-4.00 D. S. or -(-4 S. or -(-4 sph.\\nSphere, written 2 D. or 2.00 D. S. or 2 S. or 2 sph.\\n-(-Cylinder, written -(-4.00 D. C. or -(-4 C. or -(-4 cyl. (axis as indicated).\\nCylinder, written 2.00 D. C. or 2 C. or 2 cyl. (axis as indicated).\\n-(-Sphere and -(-cylinder, written -(-2.00 S. 3 +2.00 cyl. axis 90 degrees.\\nSphere and cylinder, written 2.00 S. 3 2 c yl- ax s I degrees,\\n-f Sphere and cylinder (cylinder stronger than sphere), -f 2.00 S. 3 3\u00c2\u00b0\u00c2\u00b0\\ncyl. axis 180 degrees.\\nSphere and -(-cylinder (cylinder stronger than sphere), 2.00 S. 3 +3-\u00c2\u00b0\u00c2\u00b0\\ncyl. axis 90 degrees.\\nA plus cylinder and minus cylinder may be prescribed,\\nand, if so, their axes must be at right angles to each other.\\nAn occasional exception to this may be found in irregular\\nastigmatism. Or a prism with its base indicated may be", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0060.jp2"}, "61": {"fulltext": "optics. 53\\nadded in any one of the foregoing formulas for example\\n2 S. O 2.00 cyl. axis 180C2A base in or the direc-\\ntion of the base may be abbreviated as follows B. L,\\nmeaning base in B. O., meaning base out B. U., meaning\\nbase up and B. D., meaning base down.\\nPrescriptions are never written for two spheres.\\nPrescriptions are never written for two cylinders at the\\nsame axis.\\nPrescriptions are never written for two cylinders at axes\\nother than those at right angles to each other, except, as\\njust noted, in irregular astigmatism.\\nFor obvious reasons prescriptions are never written for a\\nsphere and two cylinders except in irregular astigmatism.\\nRecognition of Lenses.\\nA convex sphere is thick at the center and thin at the\\nedge. It has the power of converging rays of light hence,\\nif strong, it is a burning glass. Objects viewed through a\\nconvex lens as it is moved before the eye, from left to\\nright and right to left or up and down, appear to move\\nin an opposite direction to that in which the lens is\\nmoved. The weaker the lens, the slower the object\\nappears to move and the stronger the lens, the faster the\\napparent movement of the object. A convex lens being a\\nmagnifier, has the effect of making objects appear larger\\nand closer when it is moved away from the observer s eye\\nor if brought toward the eye, objects already enlarged\\nappear smaller and more distant.\\nTo Find the Optic Center of a Convex Lens. Look-\\ning at a perpendicular straight line and passing a convex\\nlens before the eye from left to right has the effect of\\ndisplacing toward the right edge of the lens that portion of\\nthe line seen through the lens (see Fig. 50), and as the\\nlens is slowly moved still further to the right, the displaced", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0061.jp2"}, "62": {"fulltext": "54\\nREFRACTION AND HOW TO REFRACT.\\nportion of the line will finally coincide with the original\\nstraight line, making one continuous line through the lens.\\n(See Fig. 51.) Marking this straight\\nline on the surface of the lens, and\\nthen turning the lens to the opposite\\nmeridian and repeating the examina-\\ntion, and marking the lens as before,\\nthe optic center will be in the lens\\nbeneath the point of intersection of the\\ntwo lines. (See Fig. 52.)\\nA concave sphere is thick at the\\nedge and thin at the center, and has\\nthe power of causing rays of light\\nto diverge. When moved before the\\neye from left to right and right to left\\nor up and down, objects appear to move in the same direc-\\ntion as that in which the lens is moved.\\nA concave lens being a minifier, makes objects appear\\nFig. 50.\\nFig. 5\\nFig. 52.\\nsmaller and more distant as the glass is moved away from\\nthe eye, and if brought closer to the eye, makes objects\\napparently small appear somewhat larger and nearer.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0062.jp2"}, "63": {"fulltext": "OPTICS.\\n55\\nLooking at a straight edge or line through a concave\\nsphere, and passing the lens from left to right, the portion\\nof the line seen through the lens appears displaced toward\\nthe center of the lens (see Fig. 53), and as the lens is still\\nfurther moved to the right, the displaced portion of the\\nline finally coincides with the original straight edge, as in\\nfigure 51.\\nThe optic center of a concave lens is found in the same\\nway as the center of a convex lens.\\nA Convex Cylinder. When a convex cylinder is moved\\nFig. 53.\\nFig. 54.\\nin front of the eye in the direction of its axis, objects looked\\nat do not change their positions but when the lens is\\nmoved in the direction opposite to its axis, the movement\\nof the object is the same as that of a convex sphere. Look-\\ning at a straight edge through a convex cylinder, and\\nrotating it, has the effect of displacing away from its axis\\nthat portion of the straight edge seen through the lens.\\n(See Fig. 54.)\\nA Concave Cylinder. When a concave cylinder is\\nmoved in front of the eye in the direction of its axis, ob-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0063.jp2"}, "64": {"fulltext": "56 REFRACTION AND HOW TO REFRACT.\\njects looked at do not change their positions but when the\\nlens is moved in the direction opposite to its axis, the\\nmovement of the object is the same as that of a concave\\nsphere. Looking at a straight line through a concave\\ncylinder, and rotating it, has the effect of displacing toward\\nits axis that portion of the straight line seen through the\\nlens. (See Fig. 55.) A circle viewed through a strong con-\\ncave cylinder appears as an oval with its long diameter cor-\\nresponding to its axis. (See Fig. 56.) A circle viewed\\nthrough a strong convex cylinder appears as an oval with\\nits long diameter opposite to its axis. In place of using a\\nFig. 55. Fig. 56.\\nstraight line or straight edge to find the optic center of a\\nsphere or axis of a cylinder, two lines at right angles may\\nbe substituted (see Fig. 52) or a protractor may be used.\\nA Prism. Objects viewed through a prism are dis-\\nplaced toward its apex, and that portion of a straight line\\nseen through the prism never coincides with the straight\\nline.\\nNeutralization of Lenses. Having determined from\\nthe foregoing description what the character of an indi-\\nvidual lens may be, then to neutralize its effect or find out\\nits strength a lens of opposite character is taken from the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0064.jp2"}, "65": {"fulltext": "optics. 57\\ntrial-case and held in apposition to it, and the two lenses\\nare moved in front of the eye as a distant object is\\nobserved. That lens or combination of lenses which stops\\nall apparent movement of the object is the correct neu-\\ntralizing lens. Spherocylindric lenses are neutralized by\\nfinding out what sphere will correct one meridian and what\\nsphere will correct or neutralize the opposite meridian for\\nexample, if a minus 2 S. stops all movement in one\\nmeridian and minus 3 S. stops all movement in the other\\nmeridian, then the lens being neutralized will be plus 2 S.\\ncombined with a plus 1 cylinder. Or after a sphere neu-\\ntralizes one meridian, a cylinder may be combined until the\\nother meridian is neutralized.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0065.jp2"}, "66": {"fulltext": "CHAPTER II.\\nTHE EYE. THE STANDARD EYE. THE CARDINAL\\nPOINTS.\u00e2\u0080\u0094 VISUAL ANGLE.\u00e2\u0080\u0094 MINIMUM VISUAL AN-\\nGLE.\u00e2\u0080\u0094 STANDARD ACUTENESS OF VISION.\u00e2\u0080\u0094 SIZE OF\\nRETINAL IMAGE.\u00e2\u0080\u0094 ACCOMMODATION.\u00e2\u0080\u0094 MECHANISM\\nOF ACCOMMODATION.\u00e2\u0080\u0094 FAR AND NEAR POINTS.\u00e2\u0080\u0094\\nDETERMINATION OF DISTANT VISION AND NEAR\\nPOINT.\u00e2\u0080\u0094 AMPLITUDE OF ACCOMMODATION. CON-\\nVERGENCE.\u00e2\u0080\u0094 ANGLE GAMMA.\u00e2\u0080\u0094 ANGLE ALPHA.\\nThe Eye. While the eye is considered as the organ of\\nvision, yet its function is to form upon its retina an inverted\\nimage of any object looked at and if the retinal image is\\ndistinct, the object will appear distinct if the retinal image\\nis blurred, the object will appear blurred. By means of\\nthe optic nerve and tract the retinal impression or image\\nis placed in communication with the brain, which interprets\\nthe image and completes the visual act.\\nThe Standard Eye. For purposes of exact calcula-\\ntions it has been found necessary to project a standard or\\nschematic eye, whose nodal point (optic center) shall be\\nseven millimeters back of the anterior surface of the cor-\\nnea and fifteen millimeters from the fovea (Helmholtz).\\nAllowing one millimeter for the thickness of the choroid\\nand sclera, such an eye would have an anteroposterior\\nmeasurement of about twenty-three millimeters. Parallel\\nrays of light passing into such an eye in a state of rest\\nwould focus on the macula.\\nCardinal Points (Fig. 57). Images formed upon the\\nretina are the result of refraction by three refracting sur-\\nfaces and three refracting media. The refracting surfaces\\n58", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0066.jp2"}, "67": {"fulltext": "CARDINAL POINTS. 59\\nare .the anterior surface of the cornea and the anterior and\\nposterior surfaces of the crystalline lens. The refracting\\nmedia are the cornea (and aqueous humor forming a convex\\nlens), the crystalline lens, and the vitreous humor. These\\nrefracting surfaces and media represent a compound dioptric\\nsystem, centered upon the optic or principal axis i. e., a\\nline drawn from the pole of the cornea to a point between\\nthe nerve and fovea.\\nOn the principal axis are situated the anterior and poste-\\nrior principal foci (see p. 32), the anterior and posterior nodal\\nFig. 57.\\npoints, and the anterior and posterior principal points\u00e2\u0080\u009e The\\nanterior principal focus is situated upon the optic axis\\n1 3. 745 -[-mm. in front of the corneal apex. The pos-\\nterior principal focus is situated 15.61+ mm. back of the\\nposterior surface of the lens. The nodal points are situ-\\nated about 7 mm. back of the cornea, and correspond\\napproximately to the optic center of this compound re-\\nfracting system and as they are so close together, they are\\nconsidered as one for all purposes in the study of the for-\\nmation of images. The first or anterior principal point is", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0067.jp2"}, "68": {"fulltext": "60 REFRACTION AND HOW TO REFRACT.\\nsituated 1.75 mm. back of the anterior corneal surface, and\\nthe second or posterior principal point is situated 2.10 mm.\\nbehind the anterior surface of the cornea. The principal\\npoints are so closely situated that they are considered as\\none. The anterior focal distance equals 15.49-f- mm. and\\nthe posterior focal distance equals 20.71 -j- mm.\\nThe Visual Angle, or Angle of View. The visual angle\\nis the angle formed by rays of light from the extremes of an\\nobject passing to the nodal point of the eye or the visual\\nangle may be defined as the angle which the object subtends\\nat the nodal point of the compound refracting system of\\nthe eye. Rays of light from the extremes of an object\\nFig. 58.\\ndirected to the nodal point of the eye pass through unre-\\nfracted, and continuing their straight course, fall upon the\\nretina, forming an inverted image of the object. (See Fig.\\n5 8.)\\nThe size of the retinal image depends upon the size and\\nthe distance of the object from the nodal point of the eye.\\nObjects, therefore, which are seen under the same visual\\nangle must have the same sized retinal image. (See Fig.\\n59-)\\nIf the arrows 1, 2, 3, and 4 represented a child, a man, a\\ntree, and a church, respectively (some distance apart), they\\nwould form the same sized retinal images, and if the eye\\nwere guided alone by the size of the retinal image, it would", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0068.jp2"}, "69": {"fulltext": "MINIMUM VISUAL ANGLE.\\n61\\njudge erroneously but, by experience, distance and com-\\nparison of size are brought into consideration.\\nIf, however, arrows 2, 3, and 4 are placed at the side of\\narrow 1, then their resulting images would increase in size\\naccording to the size of their respective visual angles. (See\\nFig. 60.)\\nThe nearer an object to the eye, the larger the visual\\nFig. 59.\\nangle and retinal image the further away an object from the\\neye, the smaller the visual angle and retinal image. An ob-\\nject, to retain the same sized visual angle, must, therefore, be\\nmade larger the further it is removed from the eye this is\\ndemonstrated in figure 59, where arrow 1, to be seen\\nFig. 60.\\nunder the same visual angle which it has at present, would\\nhave to be as large as arrow 4, at the distance of arrow 4.\\nMinimum Visual Angle. This is the smallest visual\\nangle in which a standard eye can still recognize an object\\nand give it a name this angle is also spoken of as the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0069.jp2"}, "70": {"fulltext": "62 REFRACTION AND HOW TO REFRACT.\\nlimiting angle of vision. In figure 61, for example, the\\nletter D at a distance of six meters is recognized as the\\nletter D it is plainly seen but if placed beyond six meters,\\nit would form a smaller visual angle, and could not with\\ncertainty be called D.\\nTo be seen at a distance of twelve meters and still\\noccupy this same visual angle, D would have to be made\\ntwice as large i. c, the size of F and to be seen at\\ntwenty-four meters, it would have to be four times its pres-\\nent size, or the size of P. Thus, while the letter D, seen\\nclearly at six meters, would have to be made proportion-\\nately larger as it is removed from the eye, then to occupy\\nFig. 61.\\nthe same visual angle it would have to be made smaller\\nif brought closer to the eye and kept within this limiting\\nangle. In figure 61 D, F, and P can be seen closer to\\nthe eye than their respective distances call for but the pur-\\npose is to find the greatest distance from the eye at which\\nthey can be seen, as this represents the maximum acuteness\\nof vision, or maximum sharpness of sight.\\nStandard Acuteness of Vision. As it was necessary for\\npurposes of calculation to have a standard or emmetropic\\neye, so it is essential to have a standard acuteness of vision\\nwhich will be consistent with the standard or emmetropic\\neye, and thus have some method of recording numerically\\nany departure from this standard visual condition.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0070.jp2"}, "71": {"fulltext": "SIZE OF RETINAL IMAGES.\\n63\\nFig. 62.\\nm\\nFig. 63.\\nThe standard acuteness of vision is the power of the eye to\\ndistinguish letters and characters occupying an angle of five\\nminutes. Every letter is, therefore, so proportioned that it\\nwill measure just five minutes in the vertical and hori-\\nzontal meridians, and be reducible to twenty-five parts or\\nsquares, each measuring\\none minute vertically and\\nhorizontally.* (See Fig.\\n62.)\\nFigure 63 shows the\\nletter F drawn in a five-\\nminute square, and each stroke of the letter, and space\\nbetween the strokes, measuring just one minute in width.\\nAs twice the tangent of half the angle of five minutes is ex-\\npressed by the decimal .001425, then to calculate the size of\\nany letter or character which should be seen clearly and dis-\\ntinctly by the standard eye at a certain definite distance, it\\nis necessary to multiply the distance in millimeters by this\\ntangent of the angle of five minutes. Letters or characters\\nmade on this scale are called standard letters. For ex-\\nample, letters to be seen under an angle of five minutes at\\na distance of one meter (1000 mm.) would have to be\\n1.425 mm. square (1000 X .001425). At six meters\\n(6000 X .001425) 8.5 mm., etc.\\nSize of Retinal Images. The size of the retinal image\\ndepends upon two factors the size of the object itself and\\nits distance from the nodal point. In the standard eye it\\nhas been stated that the nodal point was 7 mm. back of\\nthe cornea and 1 5 mm. in front of the retina then an\\nobject 8.5 mm. square situated 6000 mm. in front of the\\nThere are two letters in the alphabet which are exceptions to this rule,\\nL and O. L can be seen under an angle of two minutes and O can be seen\\nunder an angle of three minutes.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0071.jp2"}, "72": {"fulltext": "64 REFRACTION AND HOW TO REFRACT.\\neye would have a retinal image -g-g-g-g- of 8.5, or 0.02 mm.,\\nand this is the size of the retinal image in a standard eye,\\nlooking at a standard letter at six meters distance. A good\\nrule for finding the size of the retinal image is to multiply\\nthe height of the object by the nodal distance and divide\\nby the distance. In other words, the size of the retinal\\nimage is to the size of the object as their respective dis-\\ntances from the nodal point.\\nRefraction in ophthalmology has most to do with eyes\\nwhose measurements are not according to the standard or\\nemmetropic condition, and which have their retinas closer\\nto or further from the nodal point than 1 5 mm. (spoken of\\nas ametropic). The\\nM retinal images in\\nH such eyes will be\\nsmaller in the former\\nand larger in the\\nlatter. (See Fig. 64.)\\nFig. 64. Accommodation.\\nThis may be de-\\nscribed as the power of the eye to focus rays of light upon its\\nretina from different distances at different times. In other\\nwords, the eye can not focus rays of light upon its retina from\\ndifferent points at one and the same time. For example, the\\npoint of a pencil held six inches in front of the eye is not seen\\nclearly (is hazy) as the eye looks at a printed page thirteen\\ninches beyond and, vice versa, the printed page is not seen\\ndistinctly if the point of the pencil is looked at. In the\\nstudy of convex lenses it was noticed that when an object\\nwas brought closer than infinity, the focus of the lens was\\ncorrespondingly lengthened and so, in the photographer s\\ncamera, to keep the focus on the ground-glass or sensitive\\nplate as the object is brought toward the camera, it is", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0072.jp2"}, "73": {"fulltext": "THE MECHANISM OF ACCOMMODATION. 65\\nnecessary to push the lens forward by means of the accor-\\ndion plaits but the human eye does not lengthen or\\nshorten in this way. Normally, the eyeball is inextensible,\\nand to accomplish this same purpose the ciliary muscle\\nmust contract, causing the crystalline lens to become more\\nconvex, and thus keep the rays of light entering the eye at\\na focus upon the fovea.\\nThe Mechanism of Accommodation. To appreciate\\nthis, it is necessary to understand something of the anatomy\\nof the ciliary body, of which the ciliary muscle is a part.\\nThe ciliary body is circular in form and occupies a small\\n(3 mm.) area in the eye, just beneath the sclera, at its cor-\\nneal junction. (See Fig. 57.) In section the ciliary body is\\ntriangular in shape, the base of the triangle measuring about\\n.0.8 mm. and facing toward the anterior chamber, the apex\\nof the triangle extending backward beneath the sclerotic.\\nThe ciliary body lies in apposition to the sclera, but has\\nonly a very minute attachment to it, at the sclerocorneal\\njunction, called the ligamentum annulare, or pectinatum.\\nThat portion of the ciliary body lying next to the hyaloid\\nmembrane of the vitreous humor is composed of folds,\\nknown as the ciliary processes, seventy or more in number.\\nA portion of the ciliary body is composed of muscular\\nfibers disposed in flat bundles, which interlace with each\\nother, forming a sort of plexus, and called the ciliary mus-\\ncle. This muscle, by the character of its fibers, has been\\nsubdivided into three parts (1) Meridional (2) radiating\\nand (3) circular or sphincter fibers. The meridional are\\nthe longest, lie next to the sclerotic in lamellae, parallel\\nwith it, and pass back to join the choroid coat of the eye,\\nforming what is known as the tensor choroidese, or muscle\\nof Briicke or Bowman. The radiating fibers are fan-shaped,\\nfew in number, and scattered through the ciliary body.\\n6", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0073.jp2"}, "74": {"fulltext": "66 REFRACTION AND HOW TO REFRACT.\\nThe circular or sphincter fibers also called annular are\\nsometimes referred to as the muscle of Miiller, or com-\\npressor lentis, and are the most important fibers in the\\nconsideration of accommodation they form a sphincter\\nring concentric with the equator of the lens. Attached to\\nthe ciliary body, well forward on its inner side, near the\\nbase of the triangle, is the ligament of the lens (zonule of\\nZinn), and it in turn sends fibers to the anterior and poste-\\nrior capsule of the lens. This ligament of the lens occu-\\npies an interval of about 0.5 mm. between the ciliary body\\nand the periphery of the lens, and is a constant factor in\\nall conditions of the healthy eye.\\nDuring the act of accommodation the following changes\\ntake place in the eye\\n1. The ciliary muscle contracts.\\n2. The ciliary muscle (sphincter), by contracting, makes\\na smaller circle.\\n3. The tensor choroideae draws slightly upon the choroid\\n(compressing somewhat the vitreous body), and these two\\nsets of fibers, sphincter and meridional, acting together,\\nrelax the ligament of the lens, with the result that\\n4. The lens fibers, no longer held in check, become re-\\nlaxed, and by their own inherent quality (elasticity) allow\\nthe lens to become more convex, especially on its anterior\\nsurface.\\n5. The anterior surface of the lens being made more\\nconvex, approaches the cornea.\\n6. The posterior surface of the lens becomes slightly\\nmore convex, but retains its position at the pole.\\n7. The lens axis is lengthened, but the equatorial diame-\\nter diminishes, thus keeping up the uniform interval between\\nthe equator of the lens and the ciliary body, as previously\\nreferred to. The lens does not increase in volume.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0074.jp2"}, "75": {"fulltext": "FAR POINT.\\n67\\n8. The anterior chamber becomes slightly shallower at\\nthe center and deeper in the periphery.\\n9. That portion of the iris resting upon the anterior cap-\\nsule of the lens is pushed forward, espe-\\ncially at its pupillary edge.\\n10. The iris contracts, producing a\\nsmaller pupil but it must be remembered\\nthat contraction of the iris is not an essen-\\ntial condition in accommodation. The\\nshape of the cornea is not changed during\\ncontraction of the ciliary muscle.\\nThe following table shows the compara-\\ntive measurements of a lens at rest and\\nduring the height of accommodation in a\\nhealthy emmetropic eye of ten years. The dotted lines\\nin figure 65 indicate the changes in the shape of the lens\\nat the height of accommodation.\\nFig. 65.\\nAt Rest.\\nRadius of curvature of anterior surface of lens, 10 mm.\\nposterior 6\\nDistance from anterior surface of cornea to ante-\\nrior surface of lens, 3.6\\nAnteroposterior diameter, on axis, 3.6\\nDistance from anterior surface of cornea to poste-\\nrior surface of lens, 7.2\\nEquatorial diameter, 8.7\\nHeight of\\nAccommodation.\\n6 mm.\\n5-5\\n3-2\\n4\\n7.2\\n8.2\\nFar Point. Latin, punctum remotum abbreviated p. r.\\nor r. The far point may be defined as the greatest distance\\nat which an eye has maximum sharpness of sight, or the\\nmost remote point at which the eye, in a state of rest, has\\nmaximum acuity of vision. Infinity (sign of infinity, co\\nis the far point of an emmetropic eye.\\nThe standard or emmetropic eye, when looking at distant\\nobjects, receives parallel rays of light at a focus upon its", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0075.jp2"}, "76": {"fulltext": "68 REFRACTION AND HOW TO REFRACT.\\nfovea (Fig. 66), and also emits parallel rays under these\\nconditions the ciliary muscle is not acting, the eye is in a\\ncondition of complete repose, of rest, of minimum refrac-\\ntion, and is adapted for its far point.\\nNear Point. Latin, punctum proximum abbreviated\\np. p. or p. This may be defined as the nearest point at\\nwhich an eye has maximum sharpness of sight, or the\\nnearest point to the eye at which it has distinct vision, the\\nlens is in the condition of greatest convexity, of maximum\\nrefraction.\\nAmplitude of Accommodation. This is also called the\\nrange or power f of accommodation, and may be de-\\nfined as the difference between the refraction of the eye in\\na state of rest (or adapted for its far point) and in a condi-\\ntion of maximum refraction, or adapted for its near point.\\nFor example, an emmetropic eye has infinity for its far\\npoint, and if 10 cm. distance is its near point, then the dif-\\nference between the lens adapted for infinity and 10 cm. will\\nbe io D., as 10 cm. represents the focal length, 10 D. In\\nother words, there is no accom-\\nemodation used for infinity, but\\nthere is an accommodation of\\nio D. for the near point, which\\nis the amplitude or power of\\naccommodation. The emme-\\nFig. 66. tropic eye in a state of accom-\\nmodation adds on to the ante-\\nrior surface of its lens what is equivalent to a convex\\nmeniscus. Figure 66 shows an emmetropic eye at rest\\nreceiving parallel rays of light at a focus upon its retina,\\nRange applies to the space between the far and near points,\\nf Power applies to the force or strength or diopters necessary to change\\nthe refraction from the far to the near point.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0076.jp2"}, "77": {"fulltext": "AMPLITUDE OF ACCOMMODATION.\\n6 9\\nand it also shows the same eye in its maximum state of\\naccommodation for a point 10 cm. distant; the broken\\nline representing what is equivalent to a convex meniscus,\\nadded to the anterior surface of its lens.\\nWhen the distance of the near point is known in inches\\nor centimeters, the equivalent in diopters is found by divid-\\ning 40 by the near point in inches, or by dividing 100 by\\nthe near point in centimeters. The near point being 10 cm.,\\nor 4 inches (10 into 100 or 4 into 40) the amount of accom-\\nmodation will be 10 D.\\nIn the study of healthy emmetropic eyes it has been\\nfound that the power of accommodation gradually dimin-\\nishes as the eye passes from youth to old age. This is\\nthe result of one or more changes the lens fibers lose\\ntheir elasticity, becoming sclerosed, or the ciliary muscle\\ngrows weak, or both of these changes may exist together.\\nRarely the cornea may flatten. A knowledge of the power\\nof accommodation is absolutely essential, so that any vari-\\nations from the standard condition may be noted. The fol-\\nlowing table gives the ages from ten to seventy-five years,\\nrespectively, with five-year intervals, and the near point\\nconsistent with each, as also the amplitude of accommoda-\\ntion for each period.\\nAmplitude\\nAmplitude\\nEAR.\\nNear Point.\\nin Diopters.\\nYear.\\nNear Point.\\nin Diopters\\nIO\\n7 cm.\\n14\\n45\\n28 cm.\\n3-5\\n15\\n8.5\\n12\\n5o\\n40\\n2.5\\n20\\n10\\nIO\\n55\\n55\\ni-75\\n25\\n12\\n8.5\\n60\\n100\\n1\\n30\\n14\\n7\\n65\\n133\\no-75\\n35\\n18\\n5-5\\n70\\n400\\n0.25\\n40\\n22\\n4-5\\n75\\n00\\nThis table of near points applies only to emmetropic eyes\\nor those eyes which are made emmetropic by the adjust-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0077.jp2"}, "78": {"fulltext": "70 REFRACTION AND HOW TO REFRACT.\\nment of suitable correcting lenses. The table of amplitudes,\\nhowever, is the same, with a few exceptions, for all eyes of\\nwhatever degree or amount of ametropia.\\nFor a better appreciation of the amplitude of accom-\\nmodation it is necessary to understand the two forms of\\neyes already referred to in figure 64.\\nFirst, the eye which has its retina closer to its refractive\\nmedia than the principal focus such an eye is spoken of\\nas a short or hyperopic eye. (H in Fig. 64.) (Hyperopia\\nGreek, unep, over and ^4 i e y e\\nThis eye in a state of rest (under the influence of atro-\\npin) will emit divergent rays of light, and is, therefore, in a\\nFig. 67.\\ncondition to receive only convergent rays of light at focus\\nupon its retina. (See Fig. 67.) Parallel ray$ would not\\nfocus upon the retina of such an eye, but, if possible, would\\nfocus back of the retina.\\nSecond, the eye that has its retina beyond the principal\\nfocus of its dioptric media (M in Fig. 64) such an eye is\\nspoken of as a long or myopic eye (Greek, /xvecv, to close ety,\\neye). This eye always emits convergent rays, and is, there-\\nfore, in a state to receive divergent rays of light at a focus\\nupon its retina. (See Fig. 68.) Parallel rays would not\\nfocus upon the retina of a myopic eye, but in the vitreous\\nin front of the retina.\\nThe Far Point of a Hyperopic Eye. This must neces-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0078.jp2"}, "79": {"fulltext": "FAR POINT. 7 1\\nsarily be negative (see Fig. 67), and is found by projecting\\nthe divergent emergent rays backward to the imaginary\\npoint behind the retina from which they appear to have\\ndiverged. A hyperopic eye, to receive parallel rays of\\nlight at a focus upon its retina, must, therefore, accommo-\\ndate, and the amount of accommodation thus exerted will\\nremove the near point just that much from the eye as com-\\npared with an emmetropic eye. For example, according to\\nthe table of amplitudes just given, an eye at twenty years has\\n10 D. of accommodation, but if it uses 2 D. of this to make\\nrays of light parallel, then it only has 8 D. left to accom-\\nmodate inside of infinity, with the result that the near point\\ncomes to only (8 into 100) 12.5 cm. or an eye which is\\nFig. 68.\\ntwenty-five years old has an amplitude of accommodation of\\n8.5 D., and if it has to use 4.5 D. for infinity, it would have\\n(4 into 100) a near point of 25 cm. (10 inches).\\nThe Near Point of a Hyperopic Eye. From the de-\\nscription just given it will be seen at once that the near\\npoint in hyperopic eyes is always further removed than in\\nthe emmetropic eye for a corresponding age, and that the\\nnear point depends upon the amount of accommodation\\nthat is left after the eye has accommodated for infinity.\\nThe Far Point of a Myopic Eye. This is always posi-\\ntive and situated some place inside of infinity. It is found\\nby uniting the convergent emergent rays. (See Fig. 68.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0079.jp2"}, "80": {"fulltext": "72\\nREFRACTION AND HOW TO REFRACT.\\nThe far point of a myopic eye is the result of its strong\\nrefracting power or the distance of its retina beyond the\\nprincipal focus of its dioptric media. The retina and far\\npoint of a myopic eye are conjugate foci. (See Fig. 68.)\\nThe myopic far point is equivalent to just that much refrac-\\ntion in excess of the emmetropic eye. An emmetropic eye\\nunder the influence of atropin would require a -f 2 S.\\nplaced in front of it to make rays of light focus upon its\\nretina from a distance of 50 cm., and rays of light from the\\nretina of this eye with a +2 S. in front of it would focus\\nat 50 cm. This eye, then, equals a myopic eye of 2 D.\\nThis myopic eye would have a far point of 50 cm. Where\\nthe rays of light meet as they come from a myopic eye in a\\nstate of rest is its far point.\\nThe Near Point of a Myopic Eye. This is always\\ncloser than in the emmetropic eye for a corresponding age,\\nand depends upon the distance of its far point. For exam-\\nple, an eye at twenty-five years has 8.5 D. amplitude of\\naccommodation, but if it has a far point of 70 cm., then its\\nnear point will be represented by 8.5 D. and 70 cm., i. e. t\\n1.5 D., which would equal 10 D., or a near point of 10 cm.\\nThe following table gives the comparative near points in an\\nemmetropic eye, a hyperopic eye of 2 D., and a myopic eye\\nof 2 D.\\nAge.\\n10\\n7\\n15\\n8.3\\n20\\n25\\n12\\n30\\n14\\n35\\n40\\n45\\n28\\n50\\n40\\n55\\n55\\n60\\n100\\n65\\n133\\n70\\n400\\n75\\nEmmetropia, p.p.\\n10.\\n18\\n22\\n00\\n2 D. Hyperopia,\\n8*\\n10\\n12.5\\n16\\n20\\n28. s\\n40\\n66\\n200\\n00\\n2 D. Myopia,\\n6\\n7\\n8-3\\n10\\n11\\n13\\n15-3\\n18\\n22\\n25\\n33\\n36\\n44\\n50\\nDetermining the Vision. This may be considered as\\nthe method of finding out what an eye can see without any\\nlenses placed in front of it in other words, determining the\\nvision may be defined as ascertaining the seeing quality of the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0080.jp2"}, "81": {"fulltext": "E C\\nTEST-TYPE OR TEST-LETTERS FOR DISTANT VISION. 73\\nunrefracted eye. The refraction of an eye should never be\\nconfounded with the visual quality, as refraction applies to\\nthe refractive media for example, an emmetropic eye with\\na hemorrhage at the fovea would be practically without\\nvisual quality, and yet its refraction or refractive condition\\nwould be standard. The most acute vision is at the fovea\\nand the region immediately surrounding it, but this sensi-\\nbility diminishes as the fovea is departed from and the per-\\nipheral portion of the retina approached this is due to the\\nfact that the cones are as\\nclose as 0.002 mm. at the\\nmacula, and not so close or\\nnumerous in the forepart of\\nthe eye-ground. V^ X^ V^\\nTest-type or Test-let- L 6 A O A L\\nters for Distant Vision. m\\nT G Y D GYDT\\nTo determine the vision we n\\n1 1 w u FAVHU VFHUA\\nemploy cards on which are\\nengraved test-type or letters c D p L A R E N u G L E E o I cVa\\nof various sizes, constructed t ^YcVL. A\\nso that each letter subtends a.\\nan angle of five minutes, as Fig. 69. Randall s Test-letters. Block\\n1 1 o 11 j letters in black on cream-colored\\nsuggested by Snellen, and cards-\\ndescribed on page 63\\nFigure 69 shows such cards of test-letters, reduced in size.\\nThe Roman characters just over the top of the letters indi-\\ncate the distance in meters that the letters should be seen by\\nthe standard eye, and the little figures at the left of the letters\\nindicate the equivalent distance in English feet. The top\\nletter should be seen at 60 meters, and the bottom letters\\nat 3 meters the intervening letters are to be seen at the\\nrespective distances indicated. As it is not unusual to find\\neyes that have a seeing quality better than that obtained\\n7", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0081.jp2"}, "82": {"fulltext": "74\\nREFRACTION AND HOW TO REFRACT.\\nwith Snellen s type constructed on the angle of five min-\\nutes, Dr. James Wallace has constructed letters which sub-\\ntend an angle of only four minutes. Such a card is shown\\nin figure 70 and has a large field of usefulness. While\\ntest-cards are usually white or cream-colored, with black\\nletters, Gould has white letters constructed on black\\ncards. (See Fig. 71.) As white stimu-\\nQ ates e retma an d black does not, it\\nwill be recognized at once that in one\\ninstance the card, and in the other the\\nletters, produce the retinal stimulation.\\nThe white letters seem to stand out from\\nthe black card al-\\nmost as if they were\\nembossed, giving a\\nclear-cut edge and\\nmost soothing effect\\nto the eye under ex-\\namination, and can\\nbe recognized when\\nsubtending a much\\nsmaller angle than\\nthe black letters. To\\nthis card should be\\nOOO\\nX X Y V\\n-1\\na a h\\n9 O O A\\nV V T 3 S X\\n\u00e2\u0080\u00a2AA0088JT\\nIM1S3KH\\nFig. 70. Four Min-\\nute Letters of Dr.\\nJ. Wallace. This\\ncard is constructed\\nprincipally for re-\\nflection purposes.\\n(See Fig. 3.)\\nIll\\n3 LU\\nE 111 3\\ne 3 in m\\nw 3 e m m\\ne a m n u e u\\navoid reflection,\\nhung at an angle.\\nFor aliens who do not know the\\nEnglish letters, and for illiterates, a\\nspecial card has been made, known as\\nthe illiterate or dummy card, with\\ncharacters consisting of lines shaped\\nlike the capital letter E, and made to conform to the five-\\nminute angle. As these letters are variously placed, the\\npatient is asked to tell, or indicate with his finger or fingers,\\nFig. 72.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0082.jp2"}, "83": {"fulltext": "METHOD OF PROCEDURE.\\n75\\nthe direction in which the prongs of the E point: up,\\ndown, to the right or left. This illiterate card (see Fig.\\n72) is much to be preferred to the German, Hebrew, and\\nfigure cards occasionally displayed in clinics.\\nSelection of Test-cards. The surgeon should have\\nseveral of these in duplicate with the order of the letters\\nFig. 71. Gould s Test-letters. Gothic letters in white on black cards.\\nchanged (Figs. 69, 71), as patients not infrequently and un-\\nintentionally commit them to memory. Care should be\\nexercised in the selection of test-cards, to see that each\\nletter on the card measures up to the standard square of\\nfive minutes, as many of the A s and R s and N s, etc., on\\nthe old cards as seen in the shops measure six and seven\\nminutes horizontally. It is a matter of choice with the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0083.jp2"}, "84": {"fulltext": "^6 REFRACTION AND HOW TO REFRACT.\\nsurgeon whether to use test-cards with the block or Gothic\\nletters. It is well to have both.\\nMethod of Procedure. The test-card should be hung\\non the wall with its ^j line five or six inches below the\\nlevel of the patient s eyes, and illuminated by means of\\nreflected artificial light. This is always a certain quantity,\\nwhereas daylight is too variable and not to be depended\\nupon. The patient should be placed with his back toward\\nany bright light, and at a distance of six meters from the card.\\nSometimes the surgeon s office is not six meters long, and\\nthis distance must be obtained by using diagonal corners\\nof the room or by using a plane plate-glass mirror and a\\nspecially prepared test-card with reversed letters (see Fig.\\n70), the card being hung as many meters in front of the\\nmirror as will make six meters when added to the length\\nof the office. While a distance of six meters is always to\\nbe preferred, yet if this can not be obtained, the surgeon\\nmay use a distance of four meters, but never less than this.\\nEach eye should be tested separately, the fellow-eye being\\nshielded or covered by a card or opaque disc held in front\\nof it or placed in the trial-frame. The eye should never be\\nheld shut, and any pressure upon the eyeball must be\\navoided.\\nThe record of the visual acuity is usually made in the\\nform of fractions, using Arabic or Roman notation\\nfigures usually indicate feet, and Roman letters usually sig-\\nnify meters, though there is no fixed rule for this. How-\\never expressed, the denominator indicates the size of the\\ntype which the eye reads, at the distance indicated by the\\nnumerator. For example, if at VI meters the eye reads\\nthe line of letters marked VI, then the record would be\\n^j. This would be if the numerator and denomina-\\ntor were expressed in feet. If the eye, at a distance of", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0084.jp2"}, "85": {"fulltext": "THE RECORD OF THE VISUAL ACUITY. 7\\nVI meters, reads only the letters on the XII line, then\\nthe record would be or JJ (feet). If the top letter\\nwas the only one recognized at the distance of six meters,\\nthen the record would be ^x (meters), or -gfc (feet). If\\nthe eye reads the VI line, miscalling two letters, then the\\nrecord could be made in one of three ways, each indicating\\nthe same thing. (one question mark for each\\nmiscalled letter), or partly, would indicate that\\nthe eye saw yj, but not each letter correctly. This way of\\nmaking the record is not so explicit as that with question\\nmarks. Or, f- would mean that the eye saw all of\\nVIIss J\\nand some of the letters of -J5- but this. too. is not so\\nVIIss VI\\ndefinite as the first record and the one recommended.\\nIf the eye can not recognize any letter on the card at the\\ndistance of VI meters, then the card should be brought\\ntoward the patient, or the patient told to approach the card,\\nuntil the eye can just make out the top letter and no more.\\nIf this is seen at IV meters, then the record will be if at\\none meter, the record would be etc. While it has\\nbeen stated that the visual record is usually made in the\\nform of common fractions, as just described, yet there are\\nsome who prefer to make the record in the form of deci-\\nmals namely, a vision of\u00e2\u0080\u0094 would be i.o, a vision of\\nwould be 0.50, or a vision of 375777^ would be 0.25, or a\\nvision of would be o. 1. Most authorities prefer to make\\ntheir records in the form of common fractions.\\nIn some instances the eye may not be able to distinguish\\nany letter on the card, no matter how close it may be\\nbrought to the eye, and in such a case the vision is tested\\nby holding the outstretched fingers between the patient s\\neye and a bright light (an open window), and a note is\\nmade of the greatest distance at which the eye can count", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0085.jp2"}, "86": {"fulltext": "7 8 REFRACTION AND HOW TO REFRACT.\\nfingers if at ten inches, the record would be fingers\\ncounted at ten inches, or whatever the distance may be.\\nThis ability to recognize form is spoken of as qualitative\\nlight perception. Eyes that are not able to recognize\\nform may still be able to distinguish light from darkness,\\nand this ability is tested by alternately covering and uncov-\\nering the eye as it faces a light, or as light is reflected into\\nit from a mirror. If qualitative light perception is pres-\\nent, the vision is recorded L. P., which means light per-\\nception, or the record may be made L. S., which means\\npractically the same thing, light and shade.\\nDetermining the Near Point. Having obtained and\\nrecorded the distant vision of an unrefracted eye, it is well\\nto also find out and note what is the nearest point to the\\neye at which small type may be made out this is spoken\\nof as determining the near point.\\nTest-type or Test-letters for Near Vision. To deter-\\nmine the near point, we employ cards on which are printed\\nor engraved words or sentences, or a series of letters, so\\nthat each letter in each word or sentence shall subtend an\\nangle of five minutes, at a given distance from the standard\\neye for instance, letters that are to be seen at one meter\\nand occupy the angle of five minutes, must be 1.425 mm.\\nsquare letters that are to be seen at half a meter distance\\nmust be 0.712 mm. square, etc. Most of the near cards\\nin the market are very defective in this respect, and the near\\ntypes of Jaeger are becoming obsolete, as they are not\\nstandard letters, but merely represent the various fonts of\\nprinters type. The writer s card is one of Gothic type, as\\nshown in figure 73. Another card in block letters is shown\\nin figure 74. Above each series of letters is marked the\\ngreatest distance (D) at which the respective letters maybe\\nseen; these distances vary from 0.25 to 2 meters (25 to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0086.jp2"}, "87": {"fulltext": "TEST-TYPE FOR NEAR VISION.\\n79\\nO\\nz\\n1-\\nor\\nJ\\nu\\nD\\nLl\\nz\\nJ\\no\\nz\\nq:\\nX\\nCO\\no\\n0.\\nJ\\n0)\\no\\nu\\ni\\nD\\n(0\\n0)\\no\\n(0\\nz\\n0)\\nQ\\nJ\\nX\\nU\\nL\\nO\\nD\\n0.\\nI\\nin\\nn;\\no\\nJ\\nZ\\nX\\no\\nDC\\nm\\no o\\nQ 5\\n1)\\nQ\\n(0\\nO\\nz\\nin\\nI\\n(0\\na\\no\\n10\\nq:\\n(0\\nQ.\\nX\\nX\\nX\\ni\\nO\\nj\\nh\\nDL\\nJ\\nK\\no\\nz\\nJ\\nD.\\nE\\n0\\no\\nj\\nm\\nh\\nJ\\no\\n01\\no\\nen\\n6\\nu\\na\\nN\\nO\\no\\nz\\nM\\na\\no\\nX\\no\\nu\\no\\ni\\nb.\\nH\\no\\ni-\\nb.\\nQ\\nJ\\nid\\nX\\nj\\n3\\nu.\\nO\\na.\\nI\\nu\\nH\\nIk\\nK\\nJ\\nO\\no\\nBE\\nZ\\no\\no\\nN\\nCD\\n0)\\nN\\nCO\\na\\nN\\nK\\nI\\nId\\nK\\nft\\no\\nU\\nQ.\\n1-\\nU\\nX\\nJ\\net\\nH\\nX\\no f*\\n3\\nJ\\n0.\\nT x\\no\\no\\no\\n2\\na\\nt-\\nX\\nJ\\nQ O\\nH\\nz\\nX\\nU\\nX\\nU\\nX\\nu\\na.\\no\\nz\\na\\nQ\\n2\\nn\\nin\\n(0\\nK\\nj\\na.\\no\\nx\\nz\\nz\\n1-\\n2\\nX\\nz\\n0.\\nU\\nu\\nK\\nz\\nK\\nJ\\nJ\\nI\\nJ\\nJ\\no\\nu\\nO\\na.\\nz\\na\\nK\\nz\\no\\no\\nJ\\nQ\\nX\\no\\nh-\\nO\\na\\nU\\no\\nni\\no\\n0J\\nri", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0087.jp2"}, "88": {"fulltext": "80 REFRACTION AND HOW TO REFRACT.\\n0.\\nt*\\nK\\n3\\nH\\nd\\na\\nu\\nH\\nK\\nPi\\nft\\no\\nH\\nQ\\n00\\nO\\nO)\\nt\\n00\\nen\\nt*\u00c2\u00bb\\nCO\\no\\nO\\nH\\n8\\nK\\nH\\nP\\nH\\n3 H\\nK\\no\\nin\\ni-i\\nH\\nW\\nX\\nii x\\nO\\nO\\nii\\nn\\nW\\nO\\no\\nQ\\na W\\nID\\nCD\\nCO\\nin\\n0\\nK\\nh\\nO\\no\\nH\\no\\nU\\nO\\nO\\nW\\nHi\\nP\\nX\\nft\\nH\\nK\\nH\\nft\\nJ\\nH\\nCM\\no\\niH\\nCM\\nCO\\niH\\nCM\\nCO\\n4\\no\\no\\nJ\\nX\\nH\\nX\\nJ\\nH\\nB\\nX\\no\\no\\no\\nX\\no\\nu\\nD\\nH\\np.\\nO\\no\\nQ\\nx\\nE\\nJ\\nO\\nJ\\nw\\nH\\nJj\\n\u00e2\u0096\u00a01\\n0.\\nO\\nX\\na\\nJ\\n6\\na\\no\\nJ\\nH\\nK\\nH\\nPS\\nX\\nN\\no\\n9\\na,\\nH\\nJ\\n9\\ne\u00c2\u00bb\\n00\\nat\\nr-\\nCO\\no\u00c2\u00bb\\no\\na\\nO\\no\\n|J\\nH\\nQ\\nEi\\nK\\na\\nm\\na\\na\\na\\nO\\n0*\\na\\nO J\\nH\\nK\\nJ\\nu\\nf\\no\\no.\\nH\\nX\\no a.\\n4\\n(L\\n9\\nP U\\nJ\\no\\no\\nE*\\no\\na\\nX\\n(4\\nu\\nI]\\nO\\nID\\nio\\nin\\no\\nK\\nU\\nf\\na\\nO\\na\\no\\nO\\na\\nJ;\\n\u00e2\u0096\u00a01\\nt\u00c2\u00ab\\nH\\nj\\nx\\ns\\nB\\nK\\na\\nx\\no\\na.\\nu\\nK\\nO\\nQ\\nJ\\no\\nJ\\nO\\nB\\no\\n0.\\no\\nH\\nD\\nX\\nH\\nO\\nu\\no\\nj\\nJ\\nK\\nh\\nJ\\na\\nN\\nX\\nJ\\nK\\n04\\nX\\n\u00e2\u0080\u00a24\\nM", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0088.jp2"}, "89": {"fulltext": "CONVERGENCE. 8 1\\n200 cm.), which are ample for all purposes in estimating\\nthe near point.\\nMethod of Procedure to Find the Near Point. The\\npatient is seated so that the light entering the room will\\ncome over his shoulder and fall upon the card of test-type\\nheld in front of him. The surgeon, to one side of the\\npatient, holds the card in one hand and a meter stick in the\\nother, the eye which is not being tested is covered with a\\ncard, and the patient is told to select the smallest type on\\nthe card which he can read or spell, and as he continues to\\ndo so (aloud), the surgeon gradually approaches the card\\nto the eye until the patient says that the letters commence\\nto grow hazy and he can scarcely decipher them; or\\nanother way is to hold the card close to the patient s eye\\nand gradually withdraw it until he can just recognize the\\nletters when this point is reached, the distance from the eye\\nto the card is measured with the meter stick, and this dis-\\ntance, as also the size of the type which was read, is care-\\nfully recorded. For example, the patient selecting the type\\nmarked 0.50 D. and is able to read it as close as 8 cm. and\\nno closer, the record will be near point equals type 0.50\\nD. at 8 cm. or abbreviated, would be type 0.50 D.\\n8 cm.\\nIn some instances the patient may not be able to read\\nany of the near type without the aid of a glass, and if so,\\nit will be necessary to place a plus sphere in front of the\\neye to assist in finding the near point for example, if a\\n-\\\\-2 S. was employed, then the record might be near\\npoint equals type 0.50 D. at 12 cm. with +2 S., or -J- 2\\nS. type 0.50 D. at 12 cm.\\nConvergence. Con, together, and vergere, to\\nturn literally, turning together. This is the power of the\\ninternal recti muscles (especially) to turn the eyes toward", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0089.jp2"}, "90": {"fulltext": "82\\nREFRACTION AND HOW TO REFRACT.\\nthe median line to fix an object closer than infinity.\\nStandard eyes, when looking at an object at a distance of\\nsix meters or more, are not supposed to converge the\\nvisual lines are spoken of as parallel and the power of con-\\nvergence is in a state of repose. The angle which the\\nvisual line makes in turning from infinity oo) to a near\\npoint is called the angle of convergence, and the angle\\nwhich is formed at one meter distance by the visual axis\\nwith the median line is called the meter angle, or the unit\\nof the angle of convergence. (See I, in Fig. 75.)\\nIf the visual line meets the median plane at of a\\nN\\nFig. 75.\\nmeter, it has then two-meter angles of convergence at y^\\nof a meter, four-meter angles of convergence, etc. Or\\nfive-meter angles means that the eye is converging to a\\npoint -J- of a meter distant.\\nThe size of the meter angle varies it is not the same in\\nall individuals in fact, the meter angle is smaller in children\\nthan in adults, as a rule, on account of the shorter inter-\\nocular distance. In children this distance is about 50 mm.,\\nwhereas in adults it is, on the average, 60 or 64 mm.\\nWhile standard eyes, to see a point one meter distant\\nwould converge just one meter angle, they would also\\naccommodate just one diopter to see a point at J^ of a", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0090.jp2"}, "91": {"fulltext": "NEAR POINT. 83\\nmeter they would converge just three meter angles, and at\\nthe same time would accommodate three diopters, etc.,\\nthus showing how intimately the powers of convergence and\\naccommodation are linked together, though it is possible\\nto converge without accommodation (see Presbyopia) or to\\naccommodate without convergence (paralysis of the in-\\nterni).\\nFar and Near Points of Convergence. Just as we have\\na far and a near point of accommodation, we also have a far\\nand a near point of convergence. The far point of conver-\\ngence is the point to which the visual lines are directed\\nwhen convergence is at rest, or at a minimum. The near\\nFig. 76.\\npoint of convergence is the point to which the visual lines\\nare directed when the eyes are turned inward to their\\nutmost degree.\\nInfinity, or parallelism, is the position of the visual lines\\nin the standard eyes in a state of rest (E 00, in Fig. 75).\\nVisual lines that diverge in a state of rest can only meet by\\nbeing projected backward, and, therefore, meet at an imag-\\ninary point behind the eyes (N, in Fig. 75) convergence is\\nthen spoken of as negative, or minus\\nIf the visual lines meet in a state of rest, then conver-\\ngence is spoken of as positive\\nThe amplitude of convergence is the distance measured\\nfrom the far point to the near point of convergence, and is", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0091.jp2"}, "92": {"fulltext": "8 4\\nREFRACTION AND HOW TO REFRACT.\\nrepresented by the greatest number of meter angles of con-\\nvergence which the eyes can exert.\\nAngle Gamma. An understanding of what is known as\\nthe angle gamma is important, that the observer may\\nunderstand and appreciate the real or apparent position of\\nthe eyes when looking at a near or distant point. Figure 76\\nshows the line O A (optic axis) and the optic center, or\\nnodal point (N), is situated on this line in the posterior part\\nof the crystalline lens. The line V M is really a secondary\\naxis to this dioptric system of the eye, and unites the object\\n(V) with the fovea centralis at M this line is known as the\\nvisual line. The angle\\nformed by the visual line\\nwith the optic axis at the\\nnodal point may be con-\\nsidered as the angle gam-\\nma.*\\nIf the fovea centralis at\\nM was situated on the optic\\naxis at A, then the visual\\nline and optic axis would\\ncoincide, and there would\\nnot be any angle gamma.\\nIn hyperopic and emme-\\ntropic eyes the outer ex-\\ntremity of the visual line\\nFlc _ lies 5, 7, or, in some in-\\nstances, as much as 10\\ndegrees to the nasal side of the optic axis (averaging\\nThis is not a perfectly correct statement, as the real angle gamma is the\\nangle formed by the line of fixation V R with the optic axis, R being the\\ncenter of fixation. The angle V N O and the angle V R O being so nearly\\nequal, are, for all intents and purposes, considered as the same.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0092.jp2"}, "93": {"fulltext": "ANGLE ALPHA.\\n85\\nabout 5 degrees), and is spoken of as positive, and\\ngiven the plus sign. In some long myopic eyes, however,\\nthe outer extremity of the visual line may lie to the outer\\nside of the optic axis, when it is spoken of as negative,\\nand given the minus sign.\\nTo demonstrate the angle gamma, the patient is told to\\nlook at the point of a pencil or pen held in the hand of\\nthe surgeon, about 13 inches distant (A in Figs. 77 and\\n78). If the angle gamma is positive, the eyes will appear\\ndivergent to the observer,\\nwho looks at the position\\nof the poles of the cornea\\nor centers of the pupils.\\n(See Fig. 77.)\\nIf the angle gamma is\\nnegative, the eyes will\\nappear convergent that\\nis, they appear to con-\\nverge to a point in front\\nof the pencil. (See Fig.\\n7 8.)\\nThe amount of the\\nangle gamma can be\\nmeasured by using the\\narc of the perimeter held\\nhorizontally, the patient\\nbeing placed in the same\\nposition as when having\\nhis field taken. To do this, while the eye fixes the central\\npoint, the surgeon passes a candle-flame along the arc until\\nthe catoptric image of the flame is seen at the center of the\\npupil this position of the candle-flame on the arc is noted\\nin degrees, which is the size of the angle gamma.\\nFig. 78.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0093.jp2"}, "94": {"fulltext": "86 REFRACTION AND HOW TO REFRACT.\\nAngle Alpha. This is the angle formed by the long\\naxis of the corneal ellipse with the visual axis. In the\\nconsideration of this angle it must be remembered that the\\ncornea resembles, in its central area, at least, an ellipsoid\\nof revolution, with the shortest radius usually in the verti-\\ncal meridian. The angle alpha is spoken of as positive\\nwhen the outer extremity of the long axis of the cornea is\\nto the outer side of the visual line, and negative when it\\nis to the nasal side.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0094.jp2"}, "95": {"fulltext": "CHAPTER III.\\nOPHTHALMOSCOPE.\\nDirect and Indirect Method.\\nOphthalmoscope. From oyOaXtioq, eye, and trxoneTv,\\nto observe or view literally, to view an eye. An\\ninstrument used for studying the media and interior of the\\neye. The pupil of an eye in health appears to an observer as\\nblack this is due to the fact that the observer s eye does\\nnot ordinarily intercept any of the rays of light which return\\nfrom the eye. Rays of light entering an eye are returned\\ntoward their immediate source, and, therefore, if an observer\\nwishes to see into or study the interior of an eye, he must\\nhave his own eye in the path of the returning rays. To\\naccomplish this, the observer places a mirror in front of his\\neye, so that the reflected rays entering the eye are returned\\ntoward the mirror. There is an. infinite variety of these in-\\nstruments in the market, but for the general student the\\nmodified instrument of Loring appears to meet with most\\nfavor. (See Fig. 79.)\\nThis has a concave mirror with a radius of curvature of\\n40 cm., giving a principal focus, therefore, at 20 cm. The\\nsight-hole is round and about 3 j4 mm m diameter, cut\\nthrough the glass this mirror can be tilted to an angle of\\n25 degrees. As an improvement over such a mirror, and to\\ntake its place, the writer would recommend the mirror used\\non his own ophthalmoscope, which has a radius of curvature\\nof 15 cm.; and the sight-hole, 2}4 mm. in diameter, is not\\ncut through the glass, but is made by removing the quick-\\n87", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0095.jp2"}, "96": {"fulltext": "86 REFRACTION AND HOW TO REFRACT.\\nsilver. The glass at the sight-hole gives additional reflect-\\ning surface, and at the same time does away with much\\nannoying aberration which results when the glass is per-\\nforated.\\nFRONT\\nBACK\\nFig. 79.\\nThe small sight-hole is an advantage, also, in looking\\ninto small pupils. The mirror, oblong in shape, 18 by 33\\nmm., is secured at the center of its ends, by two elevated\\nscrews, to a hollow disc 4^ cm. in diameter, in which is a\\nrevolving milled wheel, containing small spheres, each\\nabout 6 mm. in diameter. The series of spheres ranges", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0096.jp2"}, "97": {"fulltext": "OPHTHALMOSCOPE.\\n8 9\\nfrom \u00e2\u0080\u00941 D. to \u00e2\u0080\u00948 D., and from 1 D. to 7 D. The\\ncentral aperture does not contain a lens, but is left open.\\nWhen it is desirable to use any lens stronger than 8\\nD. or -f 7 D., there is an additional quadrant, which can be\\nsuperimposed and turned into place at the sight-hole it\\ncontains four lenses, 0.50 D. and 16 D., also +0.50\\nD. and +16 D. With this quadrant and the spheres in\\nthe milled wheel, any spheric combination can be made\\nfrom zero to 24 D. or to -f 23 D. An index below the\\nsight-hole of the instrument records the strength of lens\\nFig. 80.\\nthat may be in use minus lenses are usually marked in red\\nand plus lenses in white.\\nHow to Use the Ophthalmoscope. There are two ways\\nor methods by which the ophthalmoscope may be used\\nthe direct and the. indirect.\\nThe Direct Method (see Fig. 80). Proficiency with\\nthe ophthalmoscope does not come except from long and\\nconstant practice, and several important matters should\\nreceive very careful attention before the student attempts to\\nstudy the interior of an eye.\\n8", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0097.jp2"}, "98": {"fulltext": "90 REFRACTION AND HOW TO REFRACT.\\nThe Room. This should be darkened by drawing the\\nshades or closing the blinds the darker the room, the better.\\nThe Light. This should be steady, clear, and bright\\na good lamp is suitable, but an Argand burner gives more\\nintense light, and is to be preferred, especially if it is placed\\non an extension bracket that can be raised or lowered\\nand is capable of lateral movement.\\nPosition of Light and Patient. The light should be\\nseveral inches to one side and back of the patient, and on a\\nlevel with the patient s ear, so as to illuminate the outer half\\nof the eyelashes of the eye to be examined it may even\\nbe well to have the tip of the patient s nose illuminated.\\nThe patient should be seated in a comfortable chair\\n(without arms), and is instructed to look straight ahead into\\nvacancy, or at a fixed object if necessary, and is only to\\nchange the direction of his vision when told to do so.\\nUnder no circumstances should the patient be allowed to\\nlook at a light, as this will contract the pupil.\\nFor the beginner, it may be well to dilate the patient s\\npupil with a solution of cocain or homatropin. The\\nstudent, however, should learn as soon as possible to see\\ninto an eye without the aid of a mydriatic, as many patients\\nseriously object to the slight inconvenience that results\\nfrom the drugs mentioned.\\nThe Observer. If the observer has any decided refrac-\\ntive error, he should wear his correcting glasses the reason\\nfor this will be explained later. The observer should be\\nseated at the side of the patient corresponding to the eye\\nhe is to examine. Examining the right eye, the observer\\nshould be on the patient s right if the left eye, then on\\nthe patient s left.\\nWhen examining the right eye, the ophthalmoscope is\\nheld in the right hand, before the right eye and in the left", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0098.jp2"}, "99": {"fulltext": "OPHTHALMOSCOPE. 9 1\\nhand, and before the left eye, when examining the left eye.\\nThe surgeon s eye should be a little higher than the patient s.\\nPatient and observer should keep both eyes open. The\\none exception to this is when the patient has a squint,\\nwhen it will be necessary for him to cover the eye not being\\nexamined, and in this way the eye under observation will look\\nstraight ahead.\\nThe surgeon holds the ophthalmoscope perpendicularly,\\nso that the sight-hole in the mirror is directly opposite to\\nhis pupil and close to his eye. The side of the instrument\\nrests on the side of his nose or the upper margin is in the\\nhollow of the brow. The mirror is tilted toward the light.\\nThe surgeon s elbow should be at his side, and not form an\\nangle with his body.\\nWith these several details carefully executed, the surgeon\\nbegins his examination at a distance of about 25 or 30 cm.,\\nnever closer and at this distance he reflects the light from\\nthe mirror into the eye, and observes a red glare, which\\noccupies the previously black pupil. This is called the\\nreflex, and is due to the reflection from the choroidal\\ncoat of the eye. The color of the reflex varies with the size\\nof the pupil, transparency of the media, the refraction, and\\nthe amount of pigment in the eye-ground.\\nHaving obtained the reflex, it will be well for the be-\\nginner to practise keeping the reflected light upon the pupil\\nby changing his distance, approaching the eye as close as\\nan inch or two this must be done slowly, and not with a\\nrush.\\nWhat the Observer Sees. Having learned to keep the\\nlight on the pupil, the next thing is to study the transparency\\nof the media i. c, to find out if there is any interference\\nwith the free entrance and exit of the reflected rays, such\\nas would be caused by opacities in the cornea, lens, lens", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0099.jp2"}, "100": {"fulltext": "92 REFRACTION AND HOW TO REFRACT.\\ncapsule, or vitreous and, if present, to note their character\\nand exact location, whether on the visual axis or to one\\nside, etc. The next objective points will be mentioned\\nindividually, and with the idea of systematizing the study.\\nThe Optic Nerve. Also called the disc or nerve head\\nor papilla.\\nColor of the Optic Disc. This has been described as\\nresembling in color the marrow of a healthy bone, or the\\npink of a shell, etc. yet this is not by any means a true\\nstatement or description, as the apparent color of the nerve\\nis controlled in great part by the surrounding eye -ground\\nwhether this is heavily pigmented or but slightly so, or\\nwhether there is an absence of pigment, as in the albino.\\nThe student should be ready to make allowances for these\\ncontrasts.\\nThe shape of the disc varies it may appear round, oval,\\nor even irregular in outline. Usually it is a vertical oval.\\nThe vessels on the disc which carry the blood to and\\nfrom the retina are not of the same caliber, nor do they\\nhave the same curves and branches in all eyes or in the\\nsame pair of eyes. The central artery may be single or\\ndouble (if it has branched in the nerve before entering the\\neye), and enters the eye at the nasal side of the center of\\nthe disc.\\nApproximating the central artery on its temporal side is\\nthe retinal vein, which may also be double. The relative\\nnormal proportion in size between arteries and veins is\\ngenerally recognized as about two to three. The veins are\\nusually recognized by their larger size and darker color.\\nAt or near the center of the disc is often seen a depression,\\nknown as the physiologic cup this may be shallow or\\ndeep it may have shelving or abrupt edges it may even\\nbe funnel-shaped.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0100.jp2"}, "101": {"fulltext": "OPHTHALMOSCOPE. 93\\nAt the bottom of the cupping is frequently seen a gray\\nstippling, the membrana cribrosa openings in the sclera for\\nthe passage of the transparent optic nerve-fibers which go to\\nform the retina. Surrounding the disc proper is often seen\\na narrow white ring this is sclera, and is known as the\\nscleral ring. Just outside of this ring is frequently seen a\\nring of pigment this is called the choroidal ring. In many\\ncases the choroidal ring is not complete, the pigment being\\nquite irregular, or possibly there may be just one large\\nmass of pigment to one side of the disc this is not patho-\\nlogic.\\nThe retinal arteries and veins, while possessing many\\nanomalies, and while occasionally an artery and vein are\\nseen to twine around each other, usually pursue a uniform\\ncourse up and down from the disc, and are named accord-\\ningly i. e., upper nasal vein and artery upper temporal\\nvein and artery lower nasal artery and vein lower tem-\\nporal artery and vein.\\nThe retina itself, in health being transparent, is not seen.\\nThe fovea centralis, occupying the center of the macular\\nregion, is about two discs diameter to the temporal side\\nof the disc and slightly below the horizontal meridian.\\nThe fovea is recognized because it is a depression, and its\\nedges give a reflex it is very small, and appears as a bright\\nspot one or two mm. in diameter. The macular region\\nis the part of the eye-ground immediately surrounding the\\nfovea it contains minute capillaries, but it is impossible, in\\nhealthy eyes, to recognize them with the ophthalmoscope.\\nThe Choroid. This is distinguished by the character of\\nits circulation, the vessels being large, numerous, and flat-\\ntened, and without the light streak which characterizes the\\nretinal vessels. Pigment areas between the vessels are also\\ndiagnostic of this tunic. The choroidal circulation is best", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0101.jp2"}, "102": {"fulltext": "94\\nREFRACTION AND HOW TO REFRACT.\\nstudied in the blond or albino, and may be seen in many\\neyes toward the periphery of the eye-ground.\\nIn the foregoing description of the use of the ophthal-\\nmoscope, etc., it is presumed that the instrument has been\\nused without any lens in position, and that the observer s\\neye and the eye under examination are healthy emmetropic\\neyes with the accommodation at rest. Figure 8 1 shows the\\nposition of the light, L, the ophthalmoscope, the examiner s\\nand the examined eye under these conditions.\\nThe divergent rays from the light (L) are reflected con-\\nFig. Si.\\nvergently from the concave mirror, and focusing in the vitre-\\nous, they cross and form an area of illumination on the\\nretina at I V The retina, situated at the principal focus of\\nthe dioptric media, naturally projects out from its indi-\\nvidual points rays of light which are parallel as they leave\\nthe eye some of these pass through the sight-hole of the\\nmirror and meet upon the retina of the observer s emme-\\ntropic eye.\\nThere are two very important points which must be", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0102.jp2"}, "103": {"fulltext": "OPHTHALMOSCOPE.\\n95\\nconsidered when using the ophthalmoscope in the direct\\nmethod one is the direction which the rays of light take\\nas they leave the eye under examination, and the other is\\nfor the observer to keep his own eye emmetropic in other\\nwords, the observer wearing his correcting glasses should\\nnot accommodate.\\nFigure 82 shows that rays of light passing out of an eye\\ndivergently must be made parallel, so as to focus upon the\\nsurgeon s own retina (emmetropic), and to do this it is\\nFig. 82. T B indicate points at the edge of the disc from which rays pass\\nout of the eye divergently in the direction T B T B T W, and being\\nreceived by the observer s eye, are projected backward, forming an erect\\nmagnified image at T B /r This image is not so large as that seen when\\nlooking into a myopic eye. (Fig. 83.)\\nnecessary to turn a plus lens in front of the sight-hole of\\nthe ophthalmoscope the strength of the convex lens thus\\nemployed, other things being normal, is the amount of the\\nrefractive error of the eye being examined.\\nFigure 83 shows rays of light passing out of an eye\\nconvergently, and to have them parallel, so as to focus\\nupon his own retina (emmetropic), it is necessary to turn a\\nconcave lens in front of the sight-hole of the ophthalmo-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0103.jp2"}, "104": {"fulltext": "9 6\\nREFRACTION AND HOW TO REFRACT.\\nscope the strength of the concave lens thus employed,\\nother things being normal, is the amount of the refractive\\nerror of the eye under examination.\\nThe Observer s Accommodation. It has already been\\nstated that, when using the ophthalmoscope, the observer\\nshould wear any necessary correcting lenses. If the ob-\\nserver has a refractive error and does not wear his glasses,\\nhe must deduct this amount from the lens used in the\\nophthalmoscope. If he has two diopters of hyperopia\\nFig. 83. T B indicate points at the edge of the disc from which rays pass\\nout of the eye convergently in the direction T B and, being received by\\nthe observer s eye, are projected backward, forming an erect magnified\\nimage at T B This image is much larger than that seen when look-\\ning into the hyperopic eye. (Fig. 82.)\\nhimself, and the lens used in the ophthalmoscope is plus\\nfour diopters, then the eye under examination has only two\\ndiopters. It is not unusual for beginners to see the eye-\\nground (disc) in hyperopic eyes with a strong concave\\nlens this is due to the fact that they accommodate. Prac-\\ntice will overcome this habit, and it should be mastered as\\nsoon as possible. There are several ways of doing this\\none is to begin the examination at a distance of 30 or 40", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0104.jp2"}, "105": {"fulltext": "OPHTHALMOSCOPE. 97\\ncm. from the eye, with both eyes open, and to gradually\\napproach the eye as close as 3 cm., imagining all the time\\nthat one is looking for some remote point otherwise, if one\\nbegins the examination close to the eye, and imagines he is\\ngoing to see an object about an inch away, he will most\\ninvariably accommodate several diopters, with the result\\nthat he turns a strong concave lens in front of the sight-\\nhole of the ophthalmoscope to neutralize his accommodation.\\nThis explains how so many beginners diagnose all cases\\nof hyperopia as myopia. An excellent way to learn to\\nrelax the accommodation is to practise reading fine print\\nat a distance of about thirteen inches through a pair of\\nplus three lenses, placed before the surgeon s emmetropic\\neyes. Another good way to learn to relax the accommo-\\ndation is to practise on one of the many schematic eyes\\nfound in the shops. (Fig. 136.)\\nSize of the Image of the Eye-ground (Figs. 82 and\\n83). In concluding the subject of the direct method of\\nexamination it may be interesting to note the apparent size\\nof the image of the eye-ground, which, it must be remem-\\nbered, is virtual, erect, and enlarged in fact, it seems to\\nbe at. some distance behind the eye, and if the student has\\npaid close attention to the study of images as formed by\\nconvex lenses, detailed in chapter 1, he need not have any\\ndifficulty in appreciating these facts.\\nThe optic disc of an emmetropic eye, as seen through\\nthe ophthalmoscope, appears to be about 25 mm. in diam-\\neter, and about 250 mm. away. The retina of the emme-\\ntropic eye is about 1 5 mm. from its nodal point then the\\nactual size of the emmetropic disc is of 25, or J-, or\\n1.5 mm. then 15 is to 250 as 1.5 is to 25, or 16.6 the\\nmagnification, in other words, when the emmetropic disc is\\nobserved, it appears about 16.6 times larger than it actually is.\\n9", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0105.jp2"}, "106": {"fulltext": "9b REFRACTION AND HOW TO REFRACT.\\nThe Indirect Method (see Fig. 84). Practising this\\nmethod, the observer sees a larger part of the eye-ground\\nFig. 84.\\nat one time, but it is not so perfect in detail nor is it mag-\\nnified to the same extent as in the direct method. The\\nobserver does not have to get so close to his patient, which\\nis a decided advantage in some clinical cases. Unfortun-\\nately, as a preliminary\\nstep, it is often neces-\\nsary to dilate the pu-\\npil. In addition to\\nthe ophthalmoscope,\\nthere is also required\\na convex lens of\\nknown strength and\\nlarge aperture the\\none which comes in\\nthe case with the\\nscope is usually too small and too strong for general use.\\nThe writer prefers his plus 1 3 D. with metal rim and conven-\\nient handle, shown in figure 85 (reduced one-third in size).\\nFig. 85.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0106.jp2"}, "107": {"fulltext": "OPHTHALMOSCOPE. 99\\nThis is held at about three inches in front of the eye\\nunder examination, the observer resting his little and ring\\nfingers on the temple of the patient. The light may be\\nover the patient s head, or to the side corresponding to the\\neye under examination, the patient being instructed to look\\nwith both eyes open toward the surgeon s right ear when\\nthe right eye is being examined, and toward the surgeon s\\nleft ear when the left eye is examined.\\nWith a +4D. in the ophthalmoscope held close to his\\neye, the surgeon seats himself in front of the patient at\\nabout sixteen inches distant, and reflects the light through\\nthe condensing lens into the patient s eye, and then\\napproaches or moves away from the eye until he recog-\\nnizes clearly a retinal vessel or the disc he must remem-\\nber, however, that he is not looking into the eye, but is\\nviewing an aerial image formed between the convex lens\\nand the ophthalmoscope this image is not only inverted,\\nbut undergoes lateral inversion, so that the right side\\nof the disc becomes the left side of the image, and vice\\nversa the upper side of the disc becomes the lower side\\nof the image, and vice versa. As the direct method gives\\nan erect, virtual, and enlarged image, the indirect method\\nproduces an inverted, real, and small image. The principle\\nof the direct metlwd is similar to a simple microscope, and\\nthe indirect to a compound microscope.\\nThe size of the image depends upon the refraction of\\nthe eye and the distance of the convex lens from the eye\\nunder examination. In the standard eye this is always the\\nsame, no matter how far away from the eye the convex lens\\nis held. To estimate the size of the image in the standard\\neye, all that is necessaiy to know is the principal focal dis-\\ntance of the lens employed if a 13 D., then the image\\nis formed at 75 mm. (three inches), and remembering that the\\ntofC.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0107.jp2"}, "108": {"fulltext": "IOO REFRACTION AND HOW TO REFRACT.\\nretina in the eye is 15 mm. back of the nodal point, the\\nsize of the image will be to the size of the disc (if that is\\nwhat is looked at) as their respective distances, or as 15 is\\nto 75 which equals 5, the magnification.\\nThe purpose of the +4 D. in the scope is to take the\\nplace of the eye -piece in the microscope, and, therefore, to\\nmagnify the image at the same time it relieves the observer s\\naccommodation. In high myopia the +4 D. may be dis-\\npensed with.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0108.jp2"}, "109": {"fulltext": "CHAPTER IV.\\nEMMETROPIA.\u00e2\u0080\u0094 HYPEROPIA.\u00e2\u0080\u0094 MYOPIA.\\nEmmetropic\\nEmmetropia (A\u00c2\u00bb, in fiirpov, measure \u00c2\u00abvS\\neye literally means an eye in measure, or an eye which\\nhas reached that stage of development where parallel rays\\nof light will be focused on its retina without any effort of\\naccommodation. As the emmetropic eye is the ophthal-\\nmologist s ideal unit of measurement or goal in refraction,\\nthe beginner should know this form of eye thoroughly, so\\nthat he may recognize any departure from this standard\\ncondition. The emmetropic eye may be described in vari-\\nous ways, and while these descriptions may appear like\\nrepetitions, they are given for purposes of illustration\\n1. The standard or schematic eye Authorities differ\\nsomewhat in the exact measurements of a schematic eye, but\\nthe one suggested by Helm-\\nholtz is certainly worthy of\\ncareful consideration. (See\\nP 53.)\\n2. An emmetropic eye is\\none which, in. a state of rest\\n(without any effort of accom- FlG 86\\nmodation whatever), receives\\nparallel rays of light exactly at a focus upon its fovea. (See\\nFig. 86.)\\n3. An emmetropic eye, therefore, is one which, in state\\nof rest, emits parallel rays of light. (See Fig. 86.)\\n101", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0109.jp2"}, "110": {"fulltext": "102\\nREFRACTION AND HOW TO REFRACT.\\n4. An emmetropic eye is one\\nwhose fovea is situated exactly\\nat the principal focus of its re-\\nfractive system. (See Fig. 86.)\\n5. An emmetropic eye is one\\nthe vision of which, in a state\\nof rest, is adapted for infinity.\\n6. An emmetropic eye is one\\nwhich has its near point consist-\\nent with its age. (See p. 69.)\\n7. An emmetropic eye is one\\nwhich does not develop pres-\\nbyopic symptoms until forty-\\nfive or fifty years of age. (See\\np. 261.)\\n8. An emmetropic eye, in\\ncontradistinction to a myopic\\neye (see p. 1 1 3), is spoken of\\nas a healthy eye, or one which\\nshows the least amount of irri-\\ntation in its choroid and retina.\\nBecause we refer to Helm-\\nholtz s schematic eye as an em-\\nmetropic eye, it will not do to\\nsay that all eyes that measure\\njust 23 mm. in their antero-\\nposterior diameter are emme-\\ntropic (Fig. 87) for while an\\nFig. 87. 1. Emmetropia. 2. Myopia\\ndue to a strong lens. 3. Hyperopia\\ndue to a weak lens. 4. Myopia due\\nto a short radius of curvature of cornea.\\n5. Hyperopia due to a long radius of\\ncurvature of cornea. The anteropos-\\nterior diameter of all these eyes is just\\n23 mm.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0110.jp2"}, "111": {"fulltext": "AMETROPIA. IO3\\neye may be just 23 mm. in length, it may have its refractive\\nsystem stronger or weaker than is consistent with its length,\\nmaking it, if stronger, a myopic or long eye, and, if weaker,\\na short or hyperopia eye. An eye, to be emmetropic,\\ntherefore, no matter what its length, must have its refractive\\napparatus of just such strength that, in a state of rest, the\\nprincipal focus will coincide exactly with the cones at the\\nfovea. (Fig. 86.)\\nAmetropia.\\nAmetropia priv. fiirpov, a measure opt?, sight\\nliterally means an eye out of measure. An ametropic\\neye is one which, in a state of rest, does not form a distinct\\nimage of distant objects upon its retina. An ametropic\\neye may be defined as one which, in a state of rest, does\\nnot focus parallel rays of light upon its fovea. An eye\\nwhich is not emmetropic is ametropic. There are two\\nforms of ametropia axial and curvature ametropia.\\nAxial ametropia is the condition in which the dioptric\\napparatus refracts equally in all meridians, but the retina\\nof the eye, when at rest, is either closer to, or further away\\nfrom, the nodal point than the principal focus. (See Figs.\\n88 and 90.) The refraction is measured on the length of\\nthe anteroposterior axis of the eye hence its name, axial\\nametropia.\\nCurvature ametropia, in contradistinction to axial ame-\\ntropia, is the condition in which the dioptric apparatus does\\nnot refract equally in all meridians, and with the result that\\nthere is no focusing of all the rays at any one point or\\ncurvature ametropia may be considered as that condition\\nin which parallel rays of light entering an eye have two\\nfocal planes for two principal meridians at right angles to\\neach other. Curvature ametropia is commonly spoken of\\nas astigmatism. (See Chap, v.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0111.jp2"}, "112": {"fulltext": "104 REFRACTION AND HOW TO REFRACT.\\nVarieties of Axial Ametropia. Axial ametropia is of\\ntwo forms one in which the eye has its fovea closer to the\\ndioptric apparatus than its principal focus (see Fig. 88),\\nknown as the hyperopic, short, or flat eye and the other\\nform of the eye in which the fovea is further away than its\\nprincipal focus, known as the myopic or long eye. (See\\nFig. 90.)\\nHyperopia or Hypermetropia.\\nHyperopia (Mp, over axp, eye literally means\\nan eye which does not equal the standard condition, or an\\neye which is less than the standard measurement. Hyper-\\nopia is often abbreviated H. About twenty per cent,\\nof all eyes have simple hyperopia. The hyperopic eye is\\nspoken of as far-sighted, and the condition as one of far-\\nsightedness. The hyperopic eye may be described in many\\ndifferent ways\\n1. The natural eye, or the eye of nature.\\n2. The short eye. This term is used on account of\\nits fovea lying closer to the dioptric apparatus than the\\nprincipal focus.\\n3. Parallel rays of light passing into a hyperopic eye in\\na state of rest fall upon its retina or fovea before they focus.\\n(See Fig. 6j.)\\n4. Rays of light from the fovea of a hyperopic eye in a\\nstate of rest pass out divergently (see Fig. and the\\ncondition is equivalent to a convex lens refracting rays of\\nlight which proceed from a point closer to the lens than its\\nprincipal focus. (See Fig. 35.)\\n5. A hyperopic eye is one which, in a state of rest, can\\nonly receive convergent rays of light at a focus upon its\\nfovea (Fig. 88) therefore, to repeat the hyperopic eye, in\\na state of rest, emits divergent rays and receives convergent\\nrays at a focus upon its fovea.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0112.jp2"}, "113": {"fulltext": "HYPEROPIA.\\n105\\n6. As convergent rays are not found in nature, and are,\\ntherefore, artificial, a hyperopic eye is one which, in a state\\nof rest, requires a convex lens to focus parallel rays of light\\non its fovea. (See Fig. 89.)\\n7. A hyperopic eye is one which must accommodate for\\ninfinity, and, in fact, for all distances in other words, a\\nhyperopic eye in use is in a constant state of accom-\\nmodation.\\n8. A hyperopic eye having to use some of its accommo-\\ndative power for infinity, must, in consequence, have its\\nnear point removed beyond that of an emmetropic eye of\\ncorresponding age. (Seep. 71.)\\n9. From the description contained in 3, it follows that\\nFig. 89.\\nthe far point of a hyperopic eye in a state of rest is negative\\nand is found by projecting the divergent rays back-\\nward to a point behind the retina. (See Fig. 88.)\\n10. From the description contained in 6, and the descrip-\\ntion of accommodation on page 66, it is natural to find the\\nretina and choroid of many hyperopic eyes in a state of\\nirritation.\\n11. From the description contained in 6 and 7, and on\\npage 262, it follows that symptoms of presbyopia manifest\\nthemselves earlier in hyperopic than in any other form of\\neyes.\\n12. From the description contained in 5, and this may", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0113.jp2"}, "114": {"fulltext": "I06 REFRACTION AND HOW TO REFRACT.\\nappear like repetition), it follows that a hyperopic eye will\\naccept a plus glass for distant vision. (See Fig. 89.)\\n13. From 6 it is evident that the circular fibers of the\\nciliary muscle must become highly developed much more\\nso than the longitudinal fibers. Microscopically, a section\\nof the ciliary muscle on this account will bear evidence of\\nthe character of the eye from which it came.\\nCauses of Hyperopia. It is a well-known fact that the\\neyes of the new-born are, with comparatively few excep-\\ntions, hyperopic such eyes are supposed to grow in their\\nanteroposterior diameter, and at adolescence to reach that\\nstage of development called emmetropia. It is also a well-\\nknown fact that this ideal condition of emmetropia is very\\nrarely attained, the length of the eyeball not increasing in\\nproportion to the strength of its refractive system.\\nEyes may approximate the emmetropic condition, but\\nvery seldom remain so, passing into the condition in which\\nthe fovea lies beyond the principal focus, becoming what is\\nknown as long, or myopic.\\nA standard eye may be made hyperopic by removing\\nits lens the condition following cataract extraction. (See\\nFig. 161.)\\nAn eye may possibly become hyperopic in old age, from\\nflattening of the lens due to sclerosis of its fibers.\\nAny disease which will cause a flattening of the cornea\\nin a standard eye will produce hyperopia.\\nA diminution in the index of refraction of the media\\nof the standard eye will produce hyperopia.\\nSubdivisions of Hyperopia. For purposes of study\\nhyperopia has been divided into six classes or forms\\n1. Facultative hyperopia (abbreviated Hf.) is a condi-\\ntion of the eye in which the patient can overcome the error\\nby using his accommodation. It is a condition of early", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0114.jp2"}, "115": {"fulltext": "HYPEROPIA. IO7\\nlife, and is voluntary. The patient can see clearly, with or\\nwithout a convex glass.\\n2. Absolute hyperopia (abbreviated Ha.). This is hy-\\nperopia that can not be overcome by the accommodative\\neffort. It is generally a condition of old age, and is invol-\\nuntary facultative hyperopia in youth becomes absolute in\\nold age. Old age, in fact, develops every variety of\\nhyperopia. Absolute hyperopia exists whenever the defect\\nis of so high a degree that it can not be overcome by the\\naccommodation or when the accommodative power itself\\nis gone.\\n3. Relative hyperopia (abbreviated Hr.) is where ac-\\ncommodation is assisted in its efforts by the internal recti\\nmuscles in other words, the eyes squint inward.\\n4. Manifest hyperopia (abbreviated Hm.) is repre-\\nsented by the strongest convex lens through which an eye\\ncan maintain distinct distant vision. Manifest hyperopia,\\ntherefore, includes facultative and absolute.\\n5. Latent hyperopia (abbreviated HI.) is the amount\\nof hyperopia which an eye retains when a plus lens is\\nplaced in front of it. Or latent hyperopia is the difference\\nbetween the manifest hyperopia and that lens which an eye\\nwould select if its accommodation was put at rest with a\\ncycloplegic (atropin). For example, an eye accepts a\\n-f 1.25 S. as its manifest H., and, when atropin is instilled,\\nwould accept +2.75 S. for the same distant vision then\\nthe difference between the manifest +1.25 S. and +2.75\\nS. (the total) is +1.50 S., which is the latent hyper-\\nopia.\\n6. Total hyperopia (abbreviated Ht.) is the full amount\\nof the hyperopia or is represented by the strongest glass\\nwhich an eye will accept, and have clear, distinct vision\\nwhen in a state of rest.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0115.jp2"}, "116": {"fulltext": "108 REFRACTION AND HOW TO REFRACT.\\nSymptoms and Signs of Hyperopia. These are many\\nand various the principal one, however, and the one that\\ngenerally causes the patient to seek relief, is headache.\\nHeadache caused by the eyes is usually frontal, and is\\ndenominated brow ache it may be frontotemporal\\nthe pain or discomfort starting in or back of the eyes may\\nextend to the occiput or all over the head, and be accom-\\npanied with all kinds of nervous manifestations. The most\\ncharacteristic distinguishing feature of ocular headache is\\nthat it comes on while using the eyes, and gradually grows\\nworse as the use of the eyes is persisted in and, likewise,\\nthe headache gradually ceases after a few minutes or hours\\nrest of the eyes. Vertex headache, or a feeling of weight\\non the top of the head, has been preempted by the gyne-\\ncologist, and is not usually classed as ocular. The ciliary\\nmuscle being the prime factor in causing the headaches,\\nthe writer feels justified in calling it the headache mus-\\ncle. Sick headaches are largely due to eye-strain.\\nVarious functional disorders, such as dyspepsia, constipa-\\ntion, biliousness, lithemia, chorea, convulsions, epileptoid\\ndiseases, hysteria, melancholia, etc., are, according to some\\nfew authorities, attributable to this condition. See Asthen-\\nopia, page 211.\\nBlepharitis marginalis, styes, and conjunctivitis are\\nfrequently present, and in truth the hyperopic eye on\\nthis account can often be diagnosed in public outside\\nof the surgeon s office. A feeling as of sand in the eyes,\\nocular pains or postocular discomfort, a dryness of the\\nlids, as if they would stick to the eyeballs, are common\\ncomplaints, and part of the conjunctivitis. Other patients\\nhave their eyes filling with tears (epiphora) as soon as they\\nbegin reading, etc. A drowsiness or desire to sleep often\\ncomes on after or during forced accommodation.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0116.jp2"}, "117": {"fulltext": "HYPEROPIA. IO9\\nCongestion of the choroid and retina, as evidenced by the\\nophthalmoscope, often go together with the blepharitis and\\nconjunctivitis.\\nThe patient complains that the print blurs or becomes dim\\nafter reading, and this is especially apt to occur by artificial\\nlight. When the blur comes on, he has to stop and\\nrub his eyes or bathe them and then, with additional light,\\nhe is able to continue the reading for a short time longer,\\nwhen the blur again returns and the effort must be given up.\\nStrong light stimulates the accommodation. The hyper-\\nopic blur is nothing more or less than a relaxation of the\\naccommodation.\\nIn children hyperopia sometimes simulates myopia, from\\nthe fact that the child in reading holds the print very close\\nto the eyes. He does this in order to get a larger retinal\\nimage and to relieve his accommodation the retinal image\\nis not clear, and the child has to read slowly the retinal\\nimage is composed mostly of diffusion circles. The child\\nholds the print close to his eyes to avoid using his total\\naccommodation, which he might have to do if he held the\\nprint at a respectable distance.\\nHe also calls into play the orbicularis palpebrarum, and\\nnarrows the palpebral fissure, looking through a stenopeic\\nslit, as it were. These cases of simulated myopia can be\\nquickly diagnosed by\\n1. The narrow palpebral fissure during the act of reading,\\nand reading very slowly, as each letter has to be studied.\\n2. The fact that very few children have myopia.\\n3. The comparatively good distant vision, as a rule,\\nwhich myopes never have, unless the myopia is of very\\nsmall amount.\\n4. The ophthalmoscope.\\nThe beginner in ophthalmology should be on his guard", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0117.jp2"}, "118": {"fulltext": "I I O REFRACTION AND HOW TO REFRACT.\\nfor these pseudo-myopias, and not be guilty of putting\\nconcave lenses on hyperopic eyes.\\nDiagnosis of Hyperopia. This form of ametropia may\\nbe recognized in many ways\\n1. Blepharitis marginalis, if present, is generally due to\\nhyperopia.\\n2. Hyperopic eyes are said to be small, and to have\\nsmall pupils, which facts are generally confirmed but\\nmyopic eyes sometimes appear small, and have small pupils\\nalso.\\n3. A narrow face and short interpupillary distance are\\nquite indicative of hyperopia, but these indexes are not\\ninfallible.\\n4. A child with one eye turned inward toward the nose\\n(convergent squint) has hyperopic eyes, as a rule the\\nhyperopia generally not being of the same amount in the\\ntwo eyes, the squinting eye usually being the more\\nhyperopic.\\n5. It has been authoritatively stated that light-colored\\nirises are seen in hyperopic eyes and dark irises are to be\\nfound in myopic eyes, and yet this is not always correct.\\nGerman students, with their blue irises, will average from\\n50 per cent, to 60 per cent, of myopia.\\n6. Hyperopic eyes, with few exceptions, have excellent\\ndistant vision often or even better. The student should\\nbe on his guard for this, and not imagine, because a\\npatient has vision, that he is emmetropic on the con-\\ntrary, hyperopic eyes accommodate for distance, and obtain\\nthis acute vision by effort.\\n7. The patient gives a history of accommodative asthe-\\nnopia, with or without headaches coming on during or\\nafter the use of the eyes.\\n8. The distant vision of a hyperopic eye may remain", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0118.jp2"}, "119": {"fulltext": "MYOPIA. I I I\\nunchanged or may be improved with the addition of a\\nconvex lens, which latter would be impossible in emme-\\ntropia and myopia.\\n9. The near point of a hyperopic eye without glasses lies\\nbeyond that of an emmetropic eye for a corresponding age.\\n10. A hyperopic eye can see fine print clearly through a\\nconvex lens at a greater distance than its principal focus,\\nwhich would not be the case in any other form of eye.\\nOther tests for determining hyperopia are with (11) the\\nophthalmoscope, (12) the retinoscope, (13) Schemer s test,\\n(14) Thomson s ametrometer, and (15) the cobalt-blue\\nglass test, commonly spoken of as the chromo-aberration\\ntest. These tests are described in the text.\\nMyopia.\\nMyopia (,ujWv, to close Sup, eye means, liter-\\nally, to close the eye, and this origin of the name has\\narisen from the fact that many long eyes (myopic) squint\\nthe eyelids together when they endeavor to see beyond\\ntheir far point. Brachymetropia is another name for the\\nsame kind of eye. Myopia is abbreviated M. About 1.5\\nper cent, of all eyes have simple myopia. The myopic eye\\nis spoken of as near-\\nsighted, and the condition\\nas one of near-sightedness.\\nThe myopic eye may be\\ndescribed in many different\\nways\\n1. The long eye. The FlG 90\\norigin of this name is pure-\\nly anatomic, the fovea lying beyond the principal focus of\\nthe refracting system. (See Fig. 90.)\\n2. Parallel rays of light entering a myopic eye focus in", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0119.jp2"}, "120": {"fulltext": "112\\nREFRACTION AND HOW TO REFRACT.\\nthe vitreous humor before they can reach the fovea. (See\\nFig. 90.)\\n3. Rays of light from the fovea of a myopic eye pass out\\nof the eye convergently (see Figs. 68 and 91), focusing at\\nFig. 91.\\nsome point inside of infinity. The refractive condition of\\na myopic eye is similar or equivalent to a convex lens\\nrefracting rays of light which proceed from some point\\nfurther away than its principal focus. (See Fig. 33.) The\\nnearer the emergent rays of light focus to. the eye (in a\\nstate of repose), the longer the eye and the further away\\nthe emergent rays focus from the eye, the nearer the eye\\napproaches to emmetropia, or normal length.\\n4. A myopic eye is one which receives rays of light\\nwhich diverge from some point closer than six meters at a\\nfocus on its fovea and which\\nemits convergent rays. (See\\nFig. 33, and also description\\nof conjugate foci.)\\n5. As parallel rays can not\\nfocus on the fovea of a\\nmyopic eye, it is necessary to\\ngive parallel rays entering the\\neye a certain amount of divergence, so as to place the focus\\nat the fovea and to accomplish this, a concave lens must\\nbe used. (See Fig. 92.) A myopic eye, therefore, is one\\nFig. 92.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0120.jp2"}, "121": {"fulltext": "MYOPIA. 113\\nwhich requires a concave lens to improve distant vision.\\n(See Fig. 92.)\\n6. A myopic eye is one whose distant vision is made\\nworse by the addition of a convex lens.\\n7. A myopic eye is one which does not accommodate for\\ndistance.\\n8. A myopic eye having a refracting system stronger\\nthan is consistent with its length, or vice versa, greater\\nlength than is consistent with its dioptric system, naturally\\ndoes not use any accommodation except for points inside of\\nits punctum remotum, and with the result that its ampli-\\ntude of accommodation is used near by consequently, a\\nmyopic eye is one which has a near point closer than an\\nemmetropic eye of corresponding age. (See p. 72.)\\n9. From the description contained in 3 it follows that the\\nfar point of a myopic eye is positive\\n10. From the description contained in 3 and 7, it also\\nfollows that the myopic eye does not develop presbyopic\\nsymptoms until late in life.\\n1 1 From 6 and 9 it follows that the circular fibers of\\nthe ciliary muscle are not used to the same extent in a\\nmyopic eye as in the emmetropic and especially in the\\nhyperopic eye. Microscopically, a section of a ciliary\\nmuscle on this account will bear evidence of the character\\nof the eye from which it came, and have the longitudinal\\nfibers more in evidence. In some very long myopic eyes\\nthere may not be any circular fibers recognized.\\n12. Eyes in which the myopia is progressive are spoken\\nof as sick eyes.\\nCauses of Myopia. Any disease or injury which will\\nso alter the refracting system of an eye that parallel rays\\nmust focus in front of the fovea will produce the form of\\neye known as long or myopic. This may be brought about", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0121.jp2"}, "122": {"fulltext": "114 REFRACTION AND HOW TO REFRACT.\\nin different ways A shortening in the radius of curvature\\nof the cornea, such as comes with conic cornea and staphy-\\nloma of the cornea an increase in the refractive power\\nof the lens from swelling, as often precedes cataract, and\\nis spoken of as false second sight; cyclitis and irido-\\ncyclitis, which diseases cause a relaxation of the lens\\nligament, allowing the lens to assume a greater convexity\\nor ciliary spasm may produce temporarily the same con-\\ndition.\\nTechnically, however, myopia is quite universally under-\\nstood to mean a permanent elongation of the visual axis\\nof the eye beyond the principal focus of its refracting\\nsystem.\\nHeredity is certainly a predisposing factor to myopia,\\nbut this does not mean that the babe is necessarily born\\nwith long eyes. On the contrary, the eye is very likely\\nhyperopic at birth, and what the child may inherit is weak\\neye tunics. Such eyes, when placed under strain or what\\nto them is overuse, soon become elongated. This may\\nalso be brought about or assisted by poor hygienic surround-\\nings, poor health, or develop after an attack of typhoid\\nor one of the eruptive fevers.\\nThree causes for the elongation of eyes have been brought\\nforward by able authorities and expounded as theories, any\\none of which, or all three, may appear conspicuously in in-\\ndividual cases.\\n1. Anatomically, the size of the orbit and the broad\\nface give a long interpupillary distance and cause excessive\\nconvergence (turning inward of the eyes) when the eyes fix\\nat the near point.\\n2. Mechanically, when the eyes are far apart and\\nattempt to converge, the external recti muscles press upon\\nthe outer side of the globes, flattening the eyes laterally,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0122.jp2"}, "123": {"fulltext": "MYOPIA. I I 5\\nwith the result that the point of least resistance for the\\ncompressed contents of the globes is at the posterior pole\\nof the eye, and here it is that the pressure shows itself, by\\nan elongation of the eye backward in its anteroposterior\\ndiameter. This combination of the anatomic and mechanic\\ntheories may explain in great part the presence of myopia\\nin the average German student or any broad-faced indi-\\nvidual.\\n3. The inflammatory theory is that a low grade of\\ninflammation attacks the tunics of the eye, especially at\\nthe posterior pole, and is spoken of as macular chor-\\noiditis this is brought about by faulty use of the eyes,\\nin the school or in the home, in a poor light or too\\nglaring a light improperly placed, or by using the eyes\\nwith the head bent over the work so that the return circu-\\nlation from the retina and choroid is interfered with. This\\ninflammation or congestion of the tunics of the eye may\\nbe primary in itself or secondary to the anatomic and\\nmechanic causes. Be this as it may, the conditions exist,\\nand go to show more and more that myopia is actually\\nacquired and not per se congenital. The inherited con-\\ngenital anomalies of refraction, particularly astigmatism, are\\nresponsible for the myopic eye, by virtue of the pathologic\\nchanges they occasion in hard-worked eyes rather than any\\ninherited predisposition to disease. (Risley, School\\nHygiene.\\nSymptoms and Signs of Myopia. While the myope\\nmay complain of headache and symptoms of accommodative\\nasthenopia, yet the principal visual complaint will be the\\ninability to see objects distinctly which lie beyond the far\\npoint. The myope s world of clear vision is limited to the\\ndistance of the far point, where the rays of light leaving his\\neye come to a focus. Every object situated beyond the far", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0123.jp2"}, "124": {"fulltext": "I 1 6 REFRACTION AND HOW TO REFRACT.\\npoint is blurred and indistinct, and the further the object\\nfrom the far point, the more indistinct it becomes. The\\nmyopic child at school soon ranks high in the class, is fond\\nof study, of books, music, or needlework, according to the\\nsex. The myope, in other words, is usually literary in\\ntaste. Myopes avoid out-of-door sports, such as foot-ball,\\nbase-ball, golf, etc.\\nDiagnosis of Myopia. This form of ametropia may be\\nrecognized in various ways\\n1. The prominent eyeball. This is not a positive sign of\\nmyopia, though this and other signs are mentioned for the\\nreason that they are often present in the myopic condition.\\n2. The broad face and (3) long interpupillary distance\\nare quite significant of myopia, and yet the broadest face\\nwith longest interpupillary distance the writer ever saw\\nwas in a hyperopic subject.\\n4. Divergent squint usually indicates myopia, and this\\ncondition is often brought about by an inability to converge,\\nor one eye may be more myopic than its fellow, with the\\nresult that the more myopic eye turns out and soon be-\\ncomes amblyopic.\\n5. It has been stated that myopic eyes usually have\\ndark-colored irises, but this is often a fallacy, as is only too\\nevident in the German student with his blue iris.\\nThe foregoing are but signs of myopia, and are recog-\\nnized by inspection they should be looked for and care-\\nfully estimated, and each given its due consideration.\\nSubjective and objective symptoms are the true tests of\\nmyopia, and are as follows\\n6. Poor distant vision inability to see numbers on the\\nhouses across the street or on the same side of the street\\nhistory of passing friends without speaking to them. The\\nmyope enjoys close work and takes little or no interest in", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0124.jp2"}, "125": {"fulltext": "MYOPIA. I I\\nsports. A history, in other words, that is in keeping with\\na vision of short range.\\n7. Good near vision ability to see the finest print or to\\nthread the finest needle or do the finest embroidery.\\n8. The near point is closer than that of an emmetropic\\neye of corresponding age. (See p. 72.)\\n9. Distant vision is made worse by the addition of a\\nconvex lens. The writer prefers to teach the diagnosis of\\nmyopia in this way, and not to say that a concave lens\\nwill improve distant vision of course it will, but he does\\nnot want the student to put concave lenses before the\\neye of the young pseudo-myope, referred to under\\nHyperopia.\\n10. The far point is brought nearer by the addition of a\\nconvex lens. Objective methods of determining myopia\\nare by means of the\\n11. Ophthalmoscope.\\n12. Retinoscope.\\n13. Schemer s method.\\n14. Thomson s ametrometer.\\n15. Chromo-aberration test.\\nDirect Ophthalmoscopy in Axial Ametropia. Pro-\\nficiency in this method only comes by perseverance and\\nlong practice. It should not be employed to the exclusion\\nof other and more exact methods. To estimate with the\\nophthalmoscope which lens is required to give an eye\\nemmetropic vision, three very important facts should receive\\ncareful attention\\n1. The distance between the surgeon s and patient s eye.\\n2. The surgeon s and patient s accommodation.\\n3. The surgeon s own refractive error.\\nFirst, the surgeon should have his eye as close to the\\npatient s eye as possible, usually at 13 mm.; this is the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0125.jp2"}, "126": {"fulltext": "I 1 8 REFRACTION AND HOW TO REFRACT.\\nanterior principal focus of the eye, and is the distance at\\nwhich the patient will wear his glasses.\\nSecond, as already explained, the observer s and patient s\\naccommodation should be in repose. The most difficult\\npart for the student to learn is to relax his accommoda-\\ntion. The ambitious student strains his accommodation\\n(ciliary muscle) in his haste, and with the result that he\\nthinks all eyes myopic and all eye-grounds as affected\\nwith retinitis.\\nThird, the surgeon, if not emmetropic, must wear any\\nnecessary correcting lenses otherwise, the lens in the\\nophthalmoscope will record his and the patient s error\\ntogether, and deductions must be made accordingly. For\\ninstance, if the surgeon is hyperopic -\\\\-2 S., and does not\\nwear his glasses, and the ophthalmoscope records the fundus\\nas seen clearly with 5 S., this would mean that the patient\\nhad +3 S. (2 of the 5 S. being the surgeon s error); or\\nif the fundus is seen without any lens in the ophthalmoscope,\\nthen the patient s error would be 2 S. (the surgeon s\\n2 S. from o leaving 2 S.) or if the ophthalmoscope\\nshowed 2 S., then the patient s error would be 4 S.\\nor if the ophthalmoscope registered -\\\\-2 S\u00e2\u0080\u009e then the\\npatient would be emmetropic, and this -\\\\-2 S. is the sur-\\ngeon s error.\\nRules. 1. When the surgeon and patient are both hy-\\nperopic or both myopic, the surgeon must subtract his cor-\\nrection from the lens which shows at the sight-hole in the\\nophthalmoscope.\\n2. When the surgeon s eye is hyperopic or myopic, and\\nthe eye of the patient is the opposite, he must add his cor-\\nrection to the lens at the sight-hole in the ophthalmoscope.\\nWith the foregoing details clearly in mind and carefully\\nexecuted, the surgeon selects small vessels near the macula", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0126.jp2"}, "127": {"fulltext": "MYOPIA. 119\\nfor his observations. If it is impossible to see these on\\naccount of the small pupil, then he will have to observe the\\nlarger vessels at the disc (nerve-head, or papilla).\\nWhenever the vessels in the macular region are seen\\nclearly with one and the same glass in the ophthalmo-\\nscope, the refractive error can be approximated as one of\\naxial ametropia, and every three diopters, plus or minus, or\\nany multiple of three diopters, represent very closely one\\nmillimeter of lengthening or shortening of the anteropos-\\nterior diameter of the eye. For example, any eye that\\ntakes a plus 3 S. to make it emmetropic is just 1 mm. too\\nshort any eye that takes a minus 3 S. to make it emme-\\ntropic is about 1 mm. too long. It will be observed, however,\\nunder the head of curvature ametropia (astigmatism), that\\nevery 6 D. cylinder represents about 1 mm. in length, as\\nmeasured on the radius of curvature of the cornea. The\\nfollowing table, from Nettleship, gives the exact equiva-\\nlents in millimeters for axial ametropia\\nH 1 D.= o.3 mm. M I D.= o.3 mm.\\n2 D. o.5\\n3D.= o.9\\n5D.= i. 3\\n6D.= i.75\\n9D.= 2.6\\nI2D.= 3 .5\\ni8D.= 5\\nIndirect Method. See page 98 for a full description of\\nthis method. Slowly withdrawing the objective lens, and the\\ndisc remaining unchanged in size, signifies emmetropia if\\nthe disc grows uniformly smaller, it means H., and if it\\ngrows uniformly larger, it means M. (See Fig. 135.) This\\nis merely a method of diagnosis, and is never used for\\ndefinite measurements.\\n1 D.\\n0.3 mm\\n2 D.\\n0.5\\n3D-\\n1\\n5 D.\\n1-5\\n6D.\\n2\\n9 D.\\n3\\n12 D.\\n4", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0127.jp2"}, "128": {"fulltext": "CHAPTER V.\\nASTIGMATISM, OR CURVATURE AMETRO-\\nPIA.\u00e2\u0080\u0094 TESTS FOR ASTIGMATISM.\\nAstigmatism (from the Greek, priv. jriy;j.a, a\\npoint Optically, astigmatism may be defined as the re-\\nfractive condition in which rays of light from a point, pass-\\ning through a lens or series of lenses, do not focus at a point.\\nIn ophthalmology astigmatism is recognized as that con-\\ndition of the refractive system of an eye in which rays of\\nlight are not refracted equally in all meridians, and the\\nresulting image of a point becomes an oval, a line, or a\\ncircle. (See Fig. 93.)\\nOr astigmatism is that condition of an eye in which\\nthere are two principal meridians, of greatest and least\\nametropia, each having a different focus.\\nIn the standard eye the cornea is represented as a section\\nof a sphere anatomically, however, the cornea is generally\\nfound to be an ellipsoid of revolution, with its shortest\\nradius of curvature (normally 7.8 mm.) in the vertical\\nmeridian.\\nIn the study of astigmatism the meridians of minimum\\nand maximum refraction alone are considered they are\\nspoken of as the principal meridians, and are at right\\nangles to each other.\\nWith very few exceptions most eyes have some degree\\nof astigmatism. The standard or emmetropic eye is an\\nextremely rare condition, and plain myopic eyes (long eyes)\\nwithout any astigmatism are almost as rare as the emmetropic\\n120", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0128.jp2"}, "129": {"fulltext": "ASTIGMATISM.\\n121\\ncondition and while plain hyperopic eyes are seen, yet\\nstatistics show that fully eighty per cent, of hyperopic eyes\\nhave astigmatism.\\nAstigmatism is located in the cornea or lens, or it may be\\na condition of both structures in one and the same eye.\\nAstigmatism of the lens may increase, diminish, or neutral-\\nize the corneal astigmatism. Astigmatism, however, is\\nmore often a condition of the cornea than of the lens.\\nFigure 93 shows parallel rays of light passing through\\nan astigmatic lens in which the vertical meridian has the\\nFig. 93.\\nshortest radius of curvature, with the result that those rays\\nwhich pass through the vertical meridian V V 7 come to a\\nfocus before those in the horizontal meridian H H r which\\nhas the longest radius.\\nIntercepting the refracted rays at 1, 2, 3, 4, 5, and 6, the\\nimage would be at 1 a horizontal oval, at 2 a horizontal\\nline, at 3 a circle, at 4 a vertical oval, at 5 a vertical line,\\nand at 6 a vertical oval. The space between the points of\\nfoci of the two meridians (2 and 5) is known as Sturm s\\ninterval. The importance of this space or interval is that\\n11", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0129.jp2"}, "130": {"fulltext": "122 REFRACTION AND HOW TO REFRACT.\\nit represents astigmatism. Sturm s interval is the quantity\\nwhich must be found in correcting astigmatism.\\nCauses of Astigmatism. Most cases of astigmatism\\nare congenital, and some can be traced to heredity. Ac-\\nquired astigmatism may result from conic cornea, cicatrices\\nfollowing ulcers or wounds of the cornea, or be a tempo-\\nrary condition from pressure of a chalazion or other\\ngrowth and, in fact, astigmatism may develop from any\\ndisease or injury that will cause a lengthening or shortening\\nor inequality in one or more of the meridians of the cornea\\nor lens. Swelling of the different sectors of the lens will\\ncause astigmatism. The visual line not passing through\\nthe center of the cornea is a cause of astigmatism, and\\nastigmatism is the usual result following extraction of the\\nlens. Tenotomy of one or more of the extraocular mus-\\ncles will often change the corneal curvature.\\nIrregular Lenticular Astigmatism. This is a normal\\ncondition of all clear lenses. It is often infinitesimal in\\namount, and on this account does not interfere with vision.\\nIt is caused by the different sectors of the lens or by the\\nindividual lens-fibers themselves not being uniform in their\\nrefracting power. In this form of astigmatism a light does\\nnot appear to have a distinct edge, but, on the contrary,\\nthe edge has radiations passing from it, giving the light a\\nstellate appearance. There is no known glass that will\\ncorrect this variety of astigmatism.\\nPhysiologic Astigmatism. This is due to lid pressure,\\nor temporarily, to extreme pulling or contraction of the extra-\\nocular muscles. It is a voluntary astigmatism, and therefore\\nnot constant. It is not a condition of all eyes. The writer\\nhas demonstrated with the retinoscope and ophthalmometer\\nthat the condition can be produced in eyes not otherwise\\nastigmatic. Drawing the lids together in the act of squint-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0130.jp2"}, "131": {"fulltext": "ASTIGMATISM. 1 23\\ning or frowning, the patient can press the cornea from\\nabove and below, and give the horizontal meridian of the\\ncornea a longer radius of curvature and the vertical meri-\\ndian a shorter radius or with the eye looking into the\\ntelescope of the ophthalmometer, no overlapping of the\\nmires is noted, but in some instances when told to open the\\neye widely and stare into the instrument, as much as\\ny 2 or 3^ of a diopter of astigmatism may be recorded.\\nThis transient astigmatism should never be corrected\\nwith a glass.\\nSubdivisions of Astigmatism. In addition to the\\nastigmatisms just described, curvature ametropia has been\\nfurther considered as\\n1. Irregular. 6. Astigmatism against the\\n2. Regular. rule.\\n3. Symmetric. 7. Homonymous.\\n4. Asymmetric. 8. Heteronymous.\\n5. Astigmatism with the 9. Homologous.\\nrule. 10. Heterologous.\\n1. Irregular Astigmatism. This is usually located in\\nthe cornea, and is due primarily to some breach in the\\ncontinuity of one or more of its meridians for example,\\nthe vertical meridian may appear regular, but the hori-\\nzontal meridian is not a uniform curve, but is irregular at\\nsome point or points. Such meridians can not produce\\nclear retinal images, but, on the contrary, the resulting\\nretinal image is hazy or irregular.\\n2. Regular Astigmatism. In this variety the cornea\\nand lens are regular in their curvatures, from the maximum\\nto the minimum radius, and the retinal image can be made\\nclear with correcting glasses.\\nBefore entering upon the study of the various forms of\\nregular astigmatism, the student s attention is called to two", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0131.jp2"}, "132": {"fulltext": "124 REFRACTION AND HOW TO REFRACT.\\nimportant facts (a) That, as a rule, the shortest radius of\\ncurvature of the cornea is in the vertical meridian that is\\nto say, the vertical meridian has a stronger refracting power\\nthan the horizontal.\\n(U) The student should bear in mind that in the measure-\\nment of curvature ametropia each millimeter of lengthening\\nor shortening of the radius of curvature is equivalent to a\\n6 D. cylinder. For instance, an eye which requires a -j-6 D.\\ncylinder axis 90 degrees has the horizontal radius of curva-\\nture about one millimeter longer than the vertical radius\\nor an eye that requires a 6 D. cylinder axis 180 degrees\\nhas its vertical radius of curvature about one millimeter\\nshorter than the horizontal. In axial ametropia, however,\\nit was shown that every three diopter splicre represented\\nabout one millimeter in length, as measured on the axis.\\nVarieties of Regular Astigmatism. There are five\\ndifferent forms of regular astigmatism\\n[a) Simple hyperopic. (r) Compound hyperopic.\\n(6) Simple myopic. (d) Compound myopic.\\n(e) Mixed astigmatism.\\n(a) Simple Hyperopic Astigmatism. Abbreviated As.\\nH., or H. As., or Ah. About $}4 per cent, of eyes have\\nthis form of refraction. This is\\na condition where one meridian\\nof the eye is emmetropic, and\\nH the meridian at right angles to\\nit is hyperopic (see Fig. 94)\\nthe vertical meridian focuses\\n^~Z. parallel rays on the retina, and\\nthe horizontal meridian would\\nfocus back of it. The retinal image of a point is a line,\\nusually horizontal. (See 2, in Fig. 93.) The correcting\\nlens is a plus cylinder with its axis usually at 90 degrees,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0132.jp2"}, "133": {"fulltext": "ASTIGMATISM.\\n25\\nFig. 95.\\nor within 45 degrees of 90 degrees. Example, +2.00\\ncylinder axis 90 degrees.\\n(b) Simple Myopic Astigmatism. Abbreviated As. M.,\\nor M. As., or Am. This is not a common condition. About\\n1 y 2 per cent, of all eyes have this form of astigmatism.\\nThis is a condition where one meridian of the eye is emme-\\ntropic, and the meridian at right angles to it is myopic (see\\nFig. 95) the horizontal meridian\\nfocuses parallel rays on the retina,\\nand the vertical meridian focuses\\nparallel rays in front of the retina\\n(in the vitreous), with the result\\nthat they cross before reaching\\nthe retina. The retinal image of\\na point is a line, usually vertical.\\n(See Fig. 93.) The correcting lens is a minus cylinder with\\nits axis at 180 degrees, or within 45 degrees of 180 degrees.\\nExample, 2.50 cylinder axis 180 degrees.\\n(c) Compound Hyperopic Astigmatism. Abbreviated\\nH. As. Co., or Comp. Has., or H-fAh (hyperopia com-\\nbined with astigmatism hyperopic). This condition repre-\\nsents nearly forty -four per cent, of all eyes it is the most\\ncommon of all forms of re-\\nfraction.\\nThe retinal image of a\\npoint is an oval never a line\\nand never a circle. (See 1,\\nin Fig. 93.)\\nThe correcting lenses are a\\nplus sphere and a plus cylin-\\nder. Example, +2.00 S. O +3.00 cylinder axis 90 de-\\ngrees. Compound hyperopic astigmatism is a combination\\nof axial ametropia (short eye) and simple hyperopic astig-\\nFig. 96.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0133.jp2"}, "134": {"fulltext": "126 REFRACTION AND HOW TO REFRACT.\\nmatism (curvature ametropia). In this form of astigmatism\\nboth meridians have their foci back of the retina one\\nfurther back than the other. The retina intercepts the rays\\nbefore they can focus. Figure 96 shows this condition.\\nUsually the vertical meridian focuses nearer the retina than\\nthe horizontal.\\n(d) Compound Myopic Astigmatism. Abbreviated M.\\nAs. Co., or Comp. Mas., or M.-fAm. (myopia combined\\nwith astigmatism myopic). This is by far the most com-\\nmon condition of all myopic eyes, and represents about\\neight per cent, of all eyes.\\nThe retinal image of a point is always an oval never a\\nline or a circle. (See 6, in Fig.\\n93.)\\nThe correcting lenses are a\\nminus sphere and a minus cylin-\\nder. Example, 1 sph. O 2\\ncylinder axis 180 degrees. A\\ncombination of axial ametropia\\nFig. 97. (long eye) and simple myopic\\nastigmatism.\\nFigure 97 shows that parallel rays have two points of\\nfoci in front of the retina one further front than the\\nother.\\n(e) Mixed Astigmatism. This form of refraction is\\nfound in about 6*/\u00c2\u00a3 per cent, of all eyes, and is abbreviated\\nin three different ways\\n1. Ah Am. (astigmatism hyperopic with astigmatism\\nmyopic).\\n2. H+Am. (hyperopia with astigmatism myopic).\\n3. M-f-Ah. (myopia with astigmatism hyperopic).\\nThe retinal image of a point is an oval or a circle never\\na line. (See 3 and 4 in Fig. 93.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0134.jp2"}, "135": {"fulltext": "ASTIGMATISM.\\n127\\nThe correcting lenses are one of three combinations, and\\nspoken of as crossed cylinders. Examples\\n1. -j-1.00 cyl. axis 90 degrees 2.00 cyl. axis 180 degrees.\\n2. -fi S. C 3 c yl- ax i s I degrees (cylinder always stronger than the\\nsphere).\\n3. 2 S. 3 ~\\\\~3 c yl- ax i s 9\u00c2\u00b0 degrees (cylinder always stronger than the\\nsphere)\\nThe condition of mixed astigmatism is one of simple\\nhyperopic astigmatism, with simple myopic astigmatism\\none meridian focuses parallel rays in front of the retina and\\nthe other meridian (at right angles) focuses parallel rays\\nFiG.\\nFig. 99.\\nback of the retina. Figures 98 and 99 show this arrange-\\nment.\\nThe remaining subdivisions of astigmatism are merely\\nclassifications, of the different forms already described, and\\narise from a study of the axis of shortest radius of curva-\\nture.\\n3. Symmetric Astigmatism. When the combined\\nvalues, in degrees, of the meridians of shortest or longest\\nradii of curvature in both eyes equal 180 degrees (no more\\nand no less), then the astigmatism in the two eyes is spoken\\nof as symmetric. For example, if the cylinder in the right\\neye is at axis 75 degrees, and in the left eye at 105 de-\\ngrees 75 degrees and 105 degrees added together will", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0135.jp2"}, "136": {"fulltext": "128\\nREFRACTION AND HOW TO REFRACT.\\nmake 180 degrees. (See Fig. ioo.) Or if each eye takes\\na cylinder axis at 90 degrees, they are also symmetric, 90\\ndegrees and 90 degrees making 1 80 degrees. If both eyes\\nhave axes 180 degrees, they are symmetric also, one\\nmeridian being considered as zero (o).\\n4. Asymmetric astigmatism is the reverse of sym-\\nmetric, and is, therefore, the condition in which the com-\\nbined values, in degrees, of the cylinder axes do not make\\n180 degrees. For instance, if the right eye has a cylinder\\nat axis 75 degrees and the left at 120 degrees, these\\n180\\nI80 u\\n75 90\\nFig. ioo. Illustrating Symmetric Fig. ioi. Illustrating Asymmetric\\nAstigmatism. Astigmatism.\\nadded together would not make 180 degrees, but more than\\n180 degrees. (See Fig. 101.) Or, if the astigmatism in\\nthe right eye was at 35 degrees, and the left at 90 degrees,\\nthese added together would not make 180 degrees.\\nSymmetric astigmatism generally accompanies a regular\\nphysiognomy, the center of each pupil being at an equal\\ndistance from the median line of the face. Asymmetric\\nastigmatism usually accompanies an asymmetric physiog-\\nnomy, the center of one pupil being further from the\\nmedian line of the face than the other.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0136.jp2"}, "137": {"fulltext": "ASTIGMATISM.\\n129\\nMuscular insufficiency, hereafter to be described, is much\\nmore common, and, in fact, should be looked for or antici-\\npated in cases of asymmetric astigmatism.\\n5 and 6. Astigmatism with the Rule and Astigmatism\\nAgainst the Rule. Astigmatism with the rule and astig-\\nmatism against the rule refer to the condition already\\ndescribed as that in which the vertical meridian of the eye,\\nas a general rule, has the shortest radius of curvature.\\nStatistic tables on astigmatism show that most eyes\\naccept a plus cylinder at axis 90 degrees, or within 45\\n180\u00c2\u00b0\\nFig. 102. Illustrating Astigmatism FlG. 103. Illustrating Astigmatism\\nwith the rule. against the Rule.\\ndegrees (inclusive) either side of 90 degrees (see Fig.\\n102); or a minus cylinder at axis 180 degrees, or within\\n45 degrees (inclusive) either side of 180 degrees. For\\nexample, if an eye requires a plus cylinder at 45 degrees,\\nor at any axis from 45 degrees up to 135 degrees (inclu-\\nsive), taking axis 90 as the median line, then the astig-\\nmatism is with the rule. But if an eye should require a\\nplus cylinder within 45 degrees either side of 180 degrees,\\nthen the condition is one of astigmatism against the rule.\\n(See Fig. 103.) A plus or minus cylinder at 45 degrees", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0137.jp2"}, "138": {"fulltext": "130 REFRACTION AND HOW TO REFRACT.\\nor 135 degrees is recognized as astigmatism with the\\nrule.\\n7. Homonymous astigmatism is the condition in which\\nthe cylinder axis in each eye is the same.\\n8. Heteronymous astigmatism is the condition in which\\nthe astigmatism in one eye is with the rule, and in the other\\neye against the rule. For example\\nO. D. 4-2 cyl. axis 90 degrees, and O. S. -)-2.oo cyl. axis 180 degrees.\\n9. Homologous astigmatism is symmetric astigmatism\\nwith the rule i. e.\\nO. D. -)-i.oo cyl. axis 60 degrees O. S. -(-1. 00 cyl. axis 120 degrees.\\n10. Heterologous astigmatism is symmetric astigma-\\ntism against the rule i. e.\\nO. D. +1.00 cyl. axis 15 degrees, O. S. 4-1.00 cyl. axis 165 degrees.\\nMeridians of the Eye. The various axes or meridians\\nof the eye are indicated by degree markings on the peri-\\nphery of the trial-frame, and by corresponding imaginary\\nlines drawn around the eyeball from the anterior pole or\\napex of the cornea to the posterior pole.\\nEither eye (right or left) is exactly like its fellow, and is\\nnumbered by starting from zero (o) on the left-hand side of\\nthe horizontal meridian and counting downward to the right-\\nhand side until this same line is again reached. This makes\\nhalf a circle (hemisphere) of 180 degrees. (See Fig. 102.)\\nAs the degrees in this half-circle are all carried across the\\neye, they maintain their individual numbering, so that axes\\n5, 10, 15, etc., are the same whether above or below the\\nhorizontal meridian. Hence there is no reason for having\\na complete circle of 360 degrees. Some trial-frames have\\nthe upper, while others have the lower, half numbered", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0138.jp2"}, "139": {"fulltext": "ASTIGMATISM. I 3 I\\nthis makes no difference in the exact numbering in the\\none case the count is made from the left to the right, and in\\nthe other the count is made from right to left. The foreign\\ntrial-frame, as represented on page 47, may be confusing if\\nnot studied.\\nSymptoms of Astigmatism. More aggravated symp-\\ntoms of accommodative asthenopia are apt to be detailed\\nby the patient, but there are, in truth, no definite symptoms\\nwhereby the presence of astigmatism can be positively dif-\\nferentiated from axial ametropia. The diagnosis of astig-\\nmatism by the physiognomy is confirmed only because\\nmost eyes are astigmatic the simple hyperopic eye squints\\nthe eyelids together just the same as the eye that is astig-\\nmatic, so that the writer would not diagnose astigmatism\\nby the patient s individual history of his eyes.\\nHow to Diagnose Astigmatism. This is one of the\\nvery early questions of the beginner in ophthalmology.\\nAstigmatism being the prominent factor in almost all refrac-\\ntive work, the writer feels justified in giving this part of\\nrefraction extensive explanation. Of the various methods\\nof diagnosing astigmatism the writer would mention the\\nfollowing\\n1. Corneal reflex. IO. Chromo-aberration or cobalt-blue\\n2. Confusion letters. glass test.\\n3. Placido s disc. II. Thomson s ametrometer.\\n4. Stenopeic slit. 12. The ophthalmometer.\\n5. Astigmatic chart. 13. Direct ophthalmoscopy\\n6. The pointed line test. 14. Indirect ophthalmoscopy.\\n7. Perforated chart or disc. 15. Cylindric lenses.\\n8. Pray s letters. 16. Retinoscope.\\n9. Scheiner s Test.\\ni. The Corneal Reflex Test. The cornea and under-\\nlying aqueous representing a spheric mirror, naturally fur-\\nnish a small image of surrounding objects. If the cornea", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0139.jp2"}, "140": {"fulltext": "132 REFRACTION AND HOW TO REFRACT.\\nis astigmatic, the catoptric image must be correspondingly\\ndistorted. To make the examination, the patient stands\\nfacing a window, and the surgeon at one side observes the\\nimage of the window-panes in the corneal mirror these\\nwill be broadened or lengthened, or they may appear in-\\nclined to one side, according to the axis and character of\\nthe astigmatism. This test is not commonly used, is often\\noverlooked in fact, unless the astigmatism is of consid-\\nerable degree, is not a valuable test.\\n2. Confusion Letters. Letters on the card which is\\nused for testing distant vision are arranged in such order\\nthat those which have a resemblance are placed next to\\neach other. (Fig. 70.) For example, X and K, Z and E,\\nO and D, C and G, P and F, S and B, V and Y, H\\nand N, A and R, etc. The patient, in deciphering these\\nletters in the line corresponding to his best vision, often\\nmiscalls them, and can not tell an X from a K, or a Z\\nfrom an E, etc. These letters are, therefore, spoken of as\\nconfusion letters. This is a very good general test, but is\\nnot infallible, as a patient with opacities in the media will\\nmake similar mistakes.\\n3. PlacidVs Disc or Keratometer (see Fig. 104). To\\na wooden handle is secured a round piece of thin sheet-\\niron eight inches in diameter, and at its center is a small,\\nround 5 mm. opening. On one side the disc is painted\\nin alternate concentric circles or bands in black and white.\\nOn the reverse side is placed a slot to hold a convex lens\\nfor magnifying purposes. To use this disc, the patient is\\nplaced with his back to a strong light from a window, or\\nan artificial light may be placed over his head. The sur-\\ngeon holds the disc with the sight-hole close in front of\\nhis own eye, and with the light illuminating the disc, the\\npatient is instructed to look into the perforation. The sur-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0140.jp2"}, "141": {"fulltext": "ASTIGMATISM.\\n133\\ngeon then approaches the eye until the corneal image of\\nthe outer edge of the instrument corresponds to the outer\\nedge of the patient s cornea. When this distance is\\nreached, a convex 2, 3, or 4 D. sphere may be placed in\\nthe slot of the disc so as to magnify the corneal image.\\nIf the cornea is not astigmatic, then the black and white\\ncircles will appear uni-\\nform throughout but if\\nthere is astigmatism, the\\ncircles will appear more\\nor less oval. If irregu-\\nlar astigmatism or conic\\ncornea is present, the cir-\\ncles will appear broken\\nor distorted in certain\\nparts. This test has be-\\ncome almost obsolete.\\nFig. 104.\\nFig. 105.\\n4. Stenopeic Slit (see Fig. 105). This is a round metal\\ndisc of the size of the trial-lens, and contains a central slit\\nor opening about 25 mm. long and I or 2 mm. wide. The\\nstenopeic slits sold in the shops have various breadths of\\nopenings, from to 2 mm. that with the I mm. opening", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0141.jp2"}, "142": {"fulltext": "134 REFRACTION AND HOW TO REFRACT.\\nis the one recommended. The purpose of the slit is to\\ncut off or exclude all rays of light at right angles to its\\nposition in front of the eye. When placed at axis 90, all\\nrays in the horizontal meridian are excluded when placed\\nat axis 1 80, all rays in the vertical meridian are cut off, etc.\\nTo use the stenopeic slit, place it in the trial -frame in front\\nof the eye to be examined, the fellow-eye being covered.\\nThe patient is instructed to read the letters on the distant\\ntest-card, and as he does so, the slit is slowly turned\\nthrough the different meridians. If the vision remains the\\nsame, no matter through which meridian the patient reads,\\nastigmatism may be absent but if the patient selects one\\nmeridian in which he sees best, and another meridian at\\nright angles in which he does not see so well, astigmatism is\\nusually present. For instance, if the slit is at axis 75 degrees\\nand the patient reads an.d at axis 165 he reads then\\nhe is astigmatic in the 165 meridian. The amount of the\\nastigmatism can be calculated by placing spheric lenses\\nback of the slit and finding the difference in strength of\\nthe spheres which bring the vision up to the normal. For\\nexample, when the slit is at axis 75 and the patient reads\\nY\u00c2\u00a3, if a 1. 50 S. is used, and the vision becomes then\\n1.50 corrects axis 75. Turning the slit to axis 165, and\\nproceeding in the same way, if +2.50 S. brings the vision\\nfrom ^v to then +2.50 corrects axis 165, the differ-\\nence between the +1.50 and +2.50 being 1 D., and the\\nformula would be +1.50 sph. 3 -f- 1.00 cyl. axis 75\\ndegrees. This test is not often used, and when resorted\\nto, the eyes should be under the influence of a cyclo-\\nplegic. This test is of special service in some cases of\\nmixed astigmatism, irregular astigmatism, presbyopia, and\\naphakia.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0142.jp2"}, "143": {"fulltext": "ASTIGMATISM. 135\\n5. Astigmatic Chart. There is an infinite variety of\\nthese cards (see Fig. 106), and the student is puzzled\\nFig. 106. Astigmatic Charts of Dr. John Green.\\nwhich one to select. Ordinarily, the clock-dial will\\nanswer every purpose. (Fig. 107.) This is a white", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0143.jp2"}, "144": {"fulltext": "I36 REFRACTION AND HOW TO REFRACT.\\ncard with peripheral Roman characters corresponding to\\nthe characters on the clock-face, hence its name. From\\nthese figures a series of three parallel and uniformly black\\nlines, with interspaces of the same width as the lines, cross\\nfrom XII to VI, III to IX, IIII to X, V to XI, VII to I,\\nand VIII to II. This chart should be so calculated that\\nFig. 107.\\nthe lines and interspaces will form an angle of 5 minutes in\\nwidth consistent with the distance at which the test is to be\\nmade if at six meters, 8.5 mm. if at four meters, 5.7 mm.\\nIn most charts the lines subtend an angle much greater\\nthan 5 minutes for the distance at which they are used, and\\nin this way the true delicacy of the test for small errors or\\nA black card with white lines is also used. (See Fig. 108.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0144.jp2"}, "145": {"fulltext": "ASTIGMATISM.\\n137\\namounts of astigmatism is sacrificed. The purpose of the\\nchart is to detect, by the patient s answer, whether astigma-\\ntism is present, and, if so, in which meridian.\\nThe chart, illuminated by reflection from a steady artificial\\nlight, is placed on a horizontal line perpendicular to the\\npatient s eyes it should never be hung at an angle, and\\nmust always be perfectly flat. Each eye is to be tested\\nseparately. Looking at such a chart, if all the lines appear\\nFig. 108.\\nequally black, astigmatism of any considerable degree or\\namount may often be excluded but if the patient selects\\none series of lines as darker than others, then the presence\\nof astigmatism may be diagnosed. If the astigmatism is\\nof a very high degree, the patient may see the three lines\\nas one solid black line without interspaces.\\nRule i. The meridian of the eye which corresponds to\\nthe dark lines selected is the meridian of astigmatism.\\nExample. If the horizontal lines (from III to IX) appear", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0145.jp2"}, "146": {"fulltext": "I38 REFRACTION AND HOW TO REFRACT.\\ndarker than all the others, then it is the horizontal meridian\\n(o or 180 degrees) of the eye which is astigmatic. Or if\\nthe lines from VI to XII are darkest, then the vertical mer-\\nidian of the eye is astigmatic. In other words, the series\\nof darkest lines indicates the meridian of greatest ametropia.\\nRule 2. The axis of the cylinder in the prescription\\nwill be opposite to the meridian of the dark lines.\\nExample. A patient who requires a plus cylinder at axis\\n90 degrees sees the horizontal lines (from III to IX) as very\\ndark, and the lines from VI to XII not so dark, and the axis\\nof the cylinder in the prescription will be opposite to 1 80\\ndegrees i. e., at 90 degrees.\\nAccording to the definition of astigmatism with the\\nrule and astigmatism against the rule, it follows that,\\nwith few exceptions, those patients who select a series\\nof lines at 180 degrees, or within 45 degrees either side of\\n180 degrees, as darker than other lines, have hyperopic\\nastigmatism, whereas those who select a series of lines at 90\\ndegrees, or within 45 degrees either side of 90 degrees,\\nhave myopic astigmatism.\\nAccording to the definition of symmetric astigmatism, a\\npatient s right eye selecting the lines at 90 or 180 as\\ndarker than those at right angles, will select the same series\\nof dark lines in the left eye. If the series of dark lines with\\nthe right eye is from II to VIII, then the left eye selects\\nthe dark lines from X to IV, etc.\\nThe clock-dial is the form of chart in common use,\\nand as a test for astigmatism is not without considerable\\nmerit.\\nWhen the astigmatism is of small amount, it may not be\\nrecognized by means of the clock-dial until after the spheric\\ncorrection has been placed before the eye or after a cyclo-\\nplegic has been instilled.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0146.jp2"}, "147": {"fulltext": "ASTIGMATISM.\\n39\\n6. The writer s pointed line test, as shown in figure 109,\\nis a series of one-minute black squares, in three parallel\\nlines at right angles to each other, on a cream-colored card\\nthe squares and adjoining spaces making a five-minute\\nangle for six meters. By means of a clockwork and bat-\\ntery, this dial may be revolved by pressing a button. The\\nprinciple of the test is the same as the perforated disc.\\nFig. 109.\\n7. The Perforated Disc (Fig. 1 10). This is a modifica-\\ntion of the astigmatic chart. A piece of white cardboard\\nor metal, about ten inches square, has small, round perfora-\\ntions made in it of certain definite size. Each perforation is\\nseparated from its neighbor by the distance of its diameter.\\nThese openings are arranged in series of one, two, or three\\nparallel lines, exactly as in the pointed line test. This\\nchart or disc is hung on the window-pane, or an illumina-\\ntion is placed behind it. The patient, looking at the disc,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0147.jp2"}, "148": {"fulltext": "140 REFRACTION AND HOW TO REFRACT.\\nsignifies which series of perforations appear to coalesce and\\nform lines. This test is not commonly known or used. It\\nFig. iio.\\nmight be a valuable test if there was any convenient way\\nof uniformly illuminating it from behind.\\n8. Pray s Letters (Fig. in).\\n^irsr a These letters are of the Old English\\nssni a type, and composed of strokes which\\nll \u00c2\u00bbUI tl h \u00c2\u00bbM 0 run n different meridians. The pa-\\nIflmll O Mb tient lookin S at these letterS SelectS\\nthat letter which appears darker than\\n1$ Bf 8 f*\u00c2\u00ae a11 the rest The direction of the lines\\naSfcx\\\\ i\\\\\\\\v w*V in the letter selected corresponds to the\\n0*4 y^ 9 z meridian of greatest ametropia. This\\n^W sl^ test s ver y confusing to the patient,\\nFig. hi. wno sees fi rst one letter and then an-\\nother as darker than its fellows.\\nQ. Schemer* S Test. This is an old test for ametropia,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0148.jp2"}, "149": {"fulltext": "ASTIGMATISM.\\nI 4 I\\ngood in theory, but really not sufficiently accurate for prac-\\ntical purposes. It is explained for the student s information,\\nand not with the idea that he will ever take time to use it.\\nThe test is made with a small piece of metal (Fig. 112)\\nthe size of the trial-lens, which contains two pin-point round\\nopenings at its center, separated by an interval of two or\\nthree millimeters. One of these openings is covered with a\\nred glass, as suggested by Dr. Wm. Thomson. This disc\\nis placed close to the eye, so that light may pass through\\nboth openings into the eye at one and the same time. The\\neye, if not presbyopic, should be under the influence of a\\nFig. 112.\\ncycloplegic. The eye looks at a distant point of light. The\\nprinciple of the test depends upon which part of the retina\\nis stimulated by the rays entering the eye through these\\nopenings, all other rays being excluded. The student must\\nremember that rays which fall upon the temporal side of the\\nretina are referred to the nasal side those which fall upon\\nthe nasal side of the retina are referred to the temporal side\\nthose which fall upon the lower portion of the retina appear\\nto come from above and those which fall upon the upper\\nportion of the retina appear to come from below.\\nDiagnosis of Hyperopia Fig. 113). The disc is placed\\nwith the red glass (R) above. The patient then sees a red", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0149.jp2"}, "150": {"fulltext": "142\\nREFRACTION AND HOW TO REFRACT.\\nand a white light (W). The red appears below the white.\\nGradually revolving the disc, the two lights move, and keep\\nthe relative positions and distance apart. The greater the\\ndistance between the two lights, the higher the refraction\\nor amount of the hyperopia. That plus sphere placed in\\nfront of the disc which unites the two flames into one (pink)\\nflame is the approximate amount of the hyperopia.\\nDiagnosis of Myopia (Fig. 1 14). Placing the disc\\nbefore the eye as before, with\\nthe red glass (R) above, the\\npatient sees the red flame\\nabove the white (W). Gradu-\\nally revolving the disc, these\\ntwo lights keep their rela-\\ntive positions and distance.\\nThat minus sphere placed\\nbefore the disc which makes\\nthe two lights appear as one (pink) light is the approximate\\namount of the myopia.\\nDiagnosis of Emmetropia. This condition would give\\nbut one light (pink in color), and unchanged by rotating\\nthe disc.\\nDiagnosis of Simple Hyperopic Astigmatism. One\\nmeridian appears the same as in emmetropia, and the meri-\\ndian opposite to the emmetropic meridian would show a\\nseparation of the two lights, as in hyperopia. The plus cyl-\\ninder placed before the disc which unites the two lights in the\\nametropic meridian represents the amount of the astigma-\\ntism.\\nDiagnosis of Simple Myopic Astigmatism. The\\nlights are red and white in one meridian, as in simple hyper-\\nopic astigmatism, but the red light is seen in the direction\\nof the red glass, and when the disc is rotated to the oppo-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0150.jp2"}, "151": {"fulltext": "ASTIGMATISM.\\nH3\\nsite meridian, only one light appears, and of a pink color.\\nThe amount of the astigmatism is represented by the\\nstrength of minus cylinder which brings the two lights\\ntogether in the ametropic meridian.\\nDiagnosis of Compound Hyperopic Astigmatism. All\\nmeridians show two lights, the red light being in the direc-\\ntion of the clear opening in the disc, but one meridian will\\nshow a greater separation of the lights than in the meridian\\nat right angles. To find the correction and the amount of\\nthe astigmatism, proceed as in simple hyperopia, correcting\\neach meridian separately with a sphere.\\nDiagnosis of Compound Myopic Astigmatism. This\\nis the same as in compound hyperopic astigmatism, with a\\nreversal of the position of the lights, and the amount of the\\nametropia is obtained with minus spheres.\\nDiagnosis of Mixed Astigmatism. One meridian\\nappears as in simple hyperopic astigmatism, and the meri-\\ndian opposite to it appears as in simple myopic astigma-\\ntism. The amount of the astigmatism is calculated as in\\nthese two conditions.\\n10. Chromo- aberration Test. This is also known\\nas the cobalt-blue glass test. Cobalt is a mineral, and is", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0151.jp2"}, "152": {"fulltext": "144\\nREFRACTION AND HOW TO REFRACT.\\nused as a coloring-matter by glass-blowers. Cobalt-blue\\nglass comes in two forms one in which the glass is colored\\nthroughout, and the other in which it is colored on only one\\nsurface, known as flashed. To the eye, cobalt-blue glass\\nappears dark blue, but contains a great deal of red. For\\npurposes of testing ametropia, a dark shade of blue should\\nbe selected, or two or three pieces of a light shade may be\\ncemented together so as to give the desired dark shade.\\nThis glass is cut round and fitted into a trial-cell. (See\\nFigs. 1 15 and 116.)\\nThe power of cobalt-blue glass to exclude all but blue\\nFig.\\nand red rays gives this test its principle. Blue rays being\\nmore refrangible than red, naturally focus sooner than red.\\nRed rays will focus back of the blue. (See Fig. 1 17.)\\nThere are several important details in the use of this\\ntest which must be carefully executed if definite results are\\nto be obtained\\n1 The eye should be tinder the influence of a cycloplegic.\\n2. By means of a light-screen, a small round area of\\nsteady white light should be looked at from a distance of\\nfour or six meters.\\n3. Each eye is to be tested separately.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0152.jp2"}, "153": {"fulltext": "ASTIGMATISM.\\n145\\nFig. 118.\\nFig. 120.\\nFig. 121.\\nFig. 122.\\nFig. 124.\\nFig. 125.\\nFig. 126,\\nFig. 127.\\nFig. 128.\\nFig. 129.\\n18. High hyperopia. 1 19. High myopia. 120. Low simple hyperopic as-\\ntigmatism. 121. High simple hyperopic astigmatism. 122. Low simple\\nmyopic astigmatism. 123. High simple myopic astigmatism. 124. Low\\ncompound hyperopic astigmatism. 125. High compound hyperopic astig-\\nmatism. 126. Low compound myopic astigmatism. 127. High com-\\npound myopic astigmatism. 128. Low mixed astigmatism. 129. High\\nmixed astigmatism.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0153.jp2"}, "154": {"fulltext": "I46 REFRACTION AND HOW TO REFRACT.\\n4. The cobalt glass may be placed near the flame or,\\nbetter still, close in front of the patient s eye in every\\ninstance it must be perpendicular to the front of the eye,\\nand never at an angle.\\n5. All other lights except the one in use should be\\nexcluded.\\nDiagnosis of Emmetropia. Patient sees a small circle\\ncomposed of two colors equally mixed purple. (See E\\nin Fig. 11;.)\\nDiagnosis of Hyperopia (see H in Fig. 117). The\\npatient describes a red ring of light with a blue center.\\nDiagnosis of Myopia. The patient describes a blue\\nring with a red center. (See M in Fig. 117.)\\nDiagnosis of Astigmatism. If astigmatic, then he will\\ndescribe one of the conditions as shown on page 145. If\\nthe test is made as suggested, it will have three points of\\nrecommendation\\n1. The character of the refraction is quickly diagnosed.\\n2. It may lead to an early diagnosis of red-blindness, a\\ncondition often overlooked.\\n3. Likewise it will show a central scotoma for red in\\nadvanced toxic amblyopia, if the eye is made myopic with\\na plus sphere.\\n11. Thomson s Ametrometer (Fig. 130). This instru-\\nment has two small gas-flames about five millimeters in diam-\\neter, one stationary and the other movable on a metal arm,\\nwhich can be changed or revolved to any meridian. Each\\neye is tested separately at a distance of twenty feet, and\\npreferably under a cycloplegic. The method of the test is\\nto move one flame along the metal arm until the two lights\\nappear to fuse. The scale, as marked on the arm, gives\\nthe approximate strength of lens necessary to correct the\\nametropia. By raising or lowering the arm any meridian", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0154.jp2"}, "155": {"fulltext": "ASTIGMATISM.\\n147\\nmay be tested. It is a most ingenious test, but not in\\ncommon use.\\n12. The Ophthalmometer (see Figs. 131 and 132).\\nThis name literally means an eye measure, but as the in-\\nstrument only measures the different radii of corneal curva-\\nture, a much better name would be keratometer, or measure\\nof the corneal radii. The object of the ophthalmometer is\\nFig. 130.\\nthe measurement of corneal curves by means of catoptric\\nimages viewed through a telescope.\\nThe ophthalmometer consists of a telescope which con-\\ntains a Wollaston birefrangent prism placed between two bi-\\nconvex lenses. Attached to the telescope is a graduated arc,\\nupon which are placed two white enameled objects called\\nmires (targets). (See Figs. 132, 133, 134.) The left mire\\nis stationary, and is made up of two 3 cm. squares, separated", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0155.jp2"}, "156": {"fulltext": "1 48\\nREFRACTION AND HOW TO REFRACT.\\nby a black line 2 mm. wide the right mire is movable and\\ngraduated into steps, each 5 mm. wide a black line passes\\nthrough the middle of these steps. For purposes of focus-\\ning, the telescope is mounted on a movable tripod. The\\npatient is seated with his chin and forehead resting in a\\nFig. 131.\\nframe. At the side of the frame, and attached to it, are two\\nor four electric lights or Argand burners, which illuminate\\nthe mires. The surgeon, looking through the eye-piece of\\nthe telescope, focuses the center of the patient s cornea\\nuntil he sees two images of each mire clearly then he\\nselects the two central images for further study and ignores", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0156.jp2"}, "157": {"fulltext": "ASTIGMATISM. 1 49\\nthe peripheral images. Thq next step is to move the\\nright-hand mire until these two images of the mires occupy\\nthe center or pole of the cornea, so that their inner edges\\njust touch and the black line in each makes one continu-\\nous black line through both (see Fig. 133) and to do the\\nFig. 132.\\nlatter, the barrel of the telescope may have to be gradually\\nrevolved from left to right or right to left, but never more\\nthan 45 degrees either way. When this position is ob-\\ntained, the axis or meridian is noted by the arrow, which\\npoints to the figure on the dial at the back of the arc, or,\\nas in some old instruments, on the front of the dial. This", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0157.jp2"}, "158": {"fulltext": "I50 REFRACTION AND HOW TO REFRACT.\\nposition of the mires is spoken of as the primary posi-\\ntion.\\nRevolving the telescope to the opposite meridian (mer-\\nidian at right angles), which is called the secondary posi-\\ntion, the observer notes any change which may have taken\\nplace in the relative positions of the mires. If they have\\nnot changed, but still maintain their edges in apposition, as\\nin the primary position, then the cornea has a uniform cur-\\nvature thoughout, and there is no astigmatism of the\\ncornea present. If, however, when the secondary position\\nis reached and the catoptric image of the mires with the\\nsteps has encroached upon the catoptric image of the sta-\\ntionary mire, then the astigmatism is calculated by the\\namount of this overlapping.\\n(See Fig. 134.)\\nEach step representing one\\ndiopter of astigmatism, one-\\nhalf a step of overlapping\\nFig. 133. Fig. 134. would represent half a diopter,\\netc. If, in making the change\\nfrom the primary to the secondary position, the mires\\nshould separate, then the surgeon would know that his\\nsecondary position should have been his primary position,\\nand he will have to make a corresponding change.\\nAs already stated, lenticular astigmatism is not a condi-\\ntion to be ignored, as only too often it will increase,\\ndiminish, or even neutralize corneal astigmatism, so that in\\npoint of fact the ophthalmometric findings are more often\\nuseless than of real value in estimating the total refractive\\nerror. Cylinders should never be prescribed from the\\nophthalmometric findings until carefully confirmed by\\nother and much more reliable tests. As a keratometer,\\nthe instrument can not be excelled, and, therefore, it has a", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0158.jp2"}, "159": {"fulltext": "ASTIGMATISM. I 5 I\\nplace in .testing the refraction in cases of aphakia. The\\nophthalmometer as a means of diagnosis is suggestive\\nrather than positive.\\n13. Estimation of Curvature Ametropia (Astigma-\\ntism) with the Ophthalmoscope, Direct Method. The\\npresence of astigmatism is diagnosed by the direct method\\nfrom the fact that the vessels or details of the fundus are\\nnot all seen clearly with one and the same glass in the\\nophthalmoscope in other words, the vessels passing up\\nand down on the disc are seen clearly with a different lens\\nin the ophthalmoscope than is required to see the vessels\\npassing laterally or at right angles. The amount of the\\nastigmatism is the difference in the strength of the respective\\nlenses used for this purpose for instance, if the vertical\\nvessels are seen best with a -f4 S., and the horizontal\\nvessels with a -\\\\-2 S., then the amount of the astigmatism\\nwould be +2 D.\\nWhen using the ophthalmoscope for making refractive\\nestimates in astigmatic eyes, the student should remember\\nthat the glass with which a vessel is seen distinctly in one\\nmeridian represents the amount of the refraction in the\\nmeridian at right angles to this vessel. In other words,\\neach vessel in the eye-ground of an astigmatic eye is seen\\nclearest through the meridian at right angles to its course.\\nThis is a puzzle to the beginner, but he must remember that\\ncylinders refract opposite to their axes. In estimating the\\nrefraction with the ophthalmoscope, the observer looks first\\nat the shape of the disc if it appears oval, this would be an\\nevidence of astigmatism secondly, if the upper and lower\\nedges of the disc are seen clearly with a different strength\\nglass than that required to see the inner and outer margins,\\nthen this would be a further evidence of the presence of\\nastigmatism but the third and confirmatory test of the\\npresence of astigmatism should be the different strength", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0159.jp2"}, "160": {"fulltext": "152 REFRACTION AND HOW TO REFRACT.\\nglasses required to see the vessels distinctly in the neigh-\\nborhood of the macula. An eye having an oval nerve,\\nwhose edges can all be seen clearly with one and the same\\nglass in the ophthalmoscope is not usually astigmatic.\\nExamples of estimated refraction by the direct method.\\nSimple Hyperopic Astigmatism. Vertical vessels seen\\nwith a -f- 1 S. and horizontal vessels seen without any lens\\nwould equal -f i.oocyl. axis 90 degrees.\\nSimple Myopic Astigmatism. Vertical vessels seen\\nwithout any lens and horizontal vessels seen with 3 S.\\nwould equal 3 cyl. axis 180 degrees.\\nCompound Hyperopic Astigmatism. Vertical vessels\\nseen with +4 S. and horizontal vessels seen with +3 S.\\nwould equal +3.00 S. O -f- i.oocyl. axis 90 degrees.\\nCompound Myopic Astigmatism. Vertical vessels\\nseen with 2 S. and horizontal vessels seen with 5 S.\\nwould equal 2.00 S. O 3-00 cyl. axis 180 degrees.\\nMixed Astigmatism. Vertical vessels seen with\\n-f 2 S. and horizontal vessels seen with 3 S. would equal\\n3.00 S. O +5.00 cyl. axis 90 degrees.\\n14. Diagnosis of the Character of the Refraction by\\nthe Indirect Method (see Fig. 135 and p. 98). There is\\nnothing exact about this method, and the refractive error,\\nto be recognized, must be considerable.\\n1. Gradually withdrawing the lens (objective) from in\\nfront of the eye, if the aerial image of the disc retains its\\nuniform size in one meridian, it signifies emmetropia for that\\nmeridian but if it grows smaller in one meridian, that\\nmeridian is hyperopic or if larger, then that meridian is\\nmyopic.\\n2. If the image grows smaller, but more so in one meridian\\nthan the other, it signifies compound hyperopia. If the\\nimage grows larger, but more so in one meridian than the\\nother, then the condition is one of compound myopia. The", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0160.jp2"}, "161": {"fulltext": "ASTIGMATISM.\\n153\\nimage growing smaller in one meridian, while in the other\\nit grows larger, indicates mixed astigmatism.\\nFig. 135. Companion picture to figure 84. Illustrating the indirect method.\\nRays from the lamp (L) are reflected convergently from the mirror of the\\nophthalmoscope, and, passing through the convex lens and into the eye,\\nproduce a large retinal illumination, extending from I to I. TB are rays\\nfrom the edge of the disc, and, leaving the eye parallel, pass through the\\nconvex lens and form an inverted aerial image of the disc at T B The\\n-j-4 S. in the ophthalmoscope magnifies the image T W.\\n15. The cylinder lens test for astigmatism is described\\nunder Applied Refraction, page 240.\\n16. Retinoscopy is described in chapter vi.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0161.jp2"}, "162": {"fulltext": "CHAPTER VI.\\nRETINOSCOPY.\\nRetinoscopy, or the Shadow Test.\u00e2\u0080\u0094 This may be de-\\nFiG. 136. The Author s Schematic Eye for Studying Retinoscopy.\\nfined as the method of estimating the refraction of an eye\\nby reflecting into it rays of light from a plane or concave\\n154", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0162.jp2"}, "163": {"fulltext": "RETINOSCOPY.\\n155\\nmirror, and observing the movement which the retinal\\nillumination makes by rotating the mirror.\\nSuggestion. Before attempting to practise retinoscopy\\nupon the human eye, the beginner is advised to study the\\nmethod upon one of the many schematic eyes to be found\\nin the market.\\nThe principle of retinoscopy is the finding of the point\\nof reversal, or myopic far point and when an eye is emme-\\ntropic or hyperopic, it must be given a myopic far point by\\nmeans of a convex sphere. (Fig. 137.)\\n1 METER.\\nFig. 137.\\nAdvantages of Retinoscopy.\\n1. The character of the refraction is quickly diagnosed.\\n2. No expensive apparatus is necessarily required.\\n3. The refraction is estimated without the verbal assist-\\nance of the patient.\\n4. The correction is quickly obtained.\\n5. The value of retinoscopy can never be overestimated\\nin the young, in the feeble-minded, the illiterate in cases\\nof nystagmus, amblyopia, and aphakia.\\nAxiom. With an eye otherwise normal except for its\\noptic error, and under the influence of a reliable cycloplegic,\\nthere is no more exact objective method of obtaining its\\nrefraction than by retinoscopy.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0163.jp2"}, "164": {"fulltext": "1 5 6\\nREFRACTION AND HOW TO REFRACT.\\nThe surgeon should wear any necessary correcting\\nglasses and have a vision of more than otherwise he\\ncan never get satisfaction from this method. The surgeon\\nshould keep his eyes wide open and not hesitate to use his\\naccommodation, as it does not have any effect on the result,\\nas in estimating the refraction with the ophthalmoscope.\\nFig. 138. Fig. 139.\\nAuthor s Mirror with Folding Handle.\\nFlG. 138. Showing central light C, on small mirror B. This is the light the\\npatient sees when looking into the mirror, and corresponds in size to the\\none-centimeter opening in screen. D is the folding cap handle to pro-\\ntect B when not in use. A is the metal disc.\\nFig. 139. Shows the light moved to one side as a result of tilting the mirror.\\nThe patient must have his accommodation under the in-\\nfluence of a reliable cycloplegic this is imperative. Each\\neye is tested separately, and if the patient has a squint, then\\none eye should be covered while its fellow is being refracted.\\nThe patient must be comfortably seated and told to look at", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0164.jp2"}, "165": {"fulltext": "RETINOSCOPY.\\n157\\nthe metal disc of the mirror or the observer s forehead\\nabove the mirror, and never into the mirror.\\nThe Retinoscope, or Mirror. The plane mirror is 2\\ncm. in diameter on a round 4 cm. metal disc, with a 2 mm.\\nsight-hole at the center, made by removing the silvering,\\nand not by cutting a hole through the glass. (See Figs.\\n138 and 139.)\\nThe concave mirror recommended has a 25 cm. focus\\n(ten inches) and is 3 j\u00c2\u00a3 cm. in diameter\\non a metal disc of the same size as the\\nplane mirror. The sight-hole is simi-\\nlar in size and made in the same way\\nas that of the plane mirror.\\nThe light should be steady, clear,\\nand white, and secured to a movable\\nbracket. For general use, the Argand\\nburner is best.\\nThe Light-screen, or Cover-chim-\\nney. For the purpose of intercepting\\nthe heat this is made of thin asbestos,\\nand the iris diaphragm attached to it\\nregulates the amount of light desired.\\n(See Fig. 140.)\\nThe room for retinoscopy should be\\ndarkened and all sources of light except\\nthe one in use should be excluded.\\nPosition of Light and Plane Mirror. These may be\\nas close together as 6 inches or as far apart as 6 meters.\\nIt is a matter of choice with the surgeon himself where he\\nprefers to have them. The writer recommends, however,\\nhaving the rays of light come from the 10 mm. opening in\\nthe light-screen, at about 6 inches to the left and front of\\nthe surgeon, so that the rays pass in front of the left eye\\nFig. 140. Author s Iris\\nDiaphragm Chimney.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0165.jp2"}, "166": {"fulltext": "158\\nREFRACTION AND HOW TO REFRACT.\\nand fall upon the mirror held before the right eye. Some\\nsurgeons prefer having the light, with the 3 cm. opening in\\nthe screen, placed over the patient s head or to one side of\\nit. (Fig. 141.) The distance between the light and mirror\\nwill not alter the direction of the rays of light which come\\nfrom the patients eye.\\nPosition of the Light and the Concave Mirror (Figs.\\n141, 142, 143). As the purpose of the concave mirror in\\nretinoscopy is to focus rays of light before they enter the\\nI METER\\nFig. 141. Light over Patient s Head, and the Observer with Mirror at One\\nMeter Distance.\\npatient s eye, it is always necessary to have the light and\\nmirror widely separated. Usually, the light with the 3 cm.\\nopening in the screen is placed to one side or over the pa-\\ntient s head, and the surgeon with the mirror is seated about\\none meter from the patient. This will place the focus of the\\n25 cm. mirror about 33 cm. in front of the mirror.\\nDistance of Surgeon from Patient. With the plane\\nmirror he may approach within a few inches of the patient s\\neye to find the point of reversal, but with the concave mirror", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0166.jp2"}, "167": {"fulltext": "RETIXOSCOPY.\\n159\\nhe must remain at a sufficient distance to have the focus of\\nthe mirror in front of the patient s eye.\\nHow to Use the Mirror. It should be held firmly in\\nFig. 142. Illustrating High Myopia with a Concave Mirror.\\nRays of light from the lamp (L) are reflected by the mirror (m and form a\\nconjugate focus at L/, and the rays from this focal point illuminate the\\nretina at L 1 Corresponding effects result when reflection takes place\\nfrom the mirror at m /f The eye (E) behind the mirror recognizes points\\nof reversal between the eye and mirror, moving in the same direction to\\nthat in which the mirror is tilted.\\nFig. 143. Illustrating Hyperopia with the Concave Mirror.\\nThe eye (E) recognizes a virtual image behind the eye under examination, so\\nthat when the mirror is focusing the rays from the lamp (L) at L\\nthe upper portion of the retina is illuminated, and vice versa, when the\\nmirror (\u00c2\u00bbi is focusing the rays at L 9 the lower portion of the retina is\\nilluminated. The retinal illumination moves opposite to that of the mirror.\\nthe right hand before the right eye, so that the sight-hole\\nis opposite to the observer s pupil. The movements im-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0167.jp2"}, "168": {"fulltext": "l6o REFRACTION AND HOW TO REFRACT.\\nparted to the mirror must be limited, though they may be\\nquick or slow, but never at any time should the mirror be\\ntilted more than 2 or 3 mm., otherwise the light will be lost\\nfrom the eye.\\nWhat the Observer Sees, or the general appearance\\nof the reflection from the eye. The reflex from the pupil\\nvaries in different patients, and is subject to many changes\\nas the refraction is altered by correcting glasses, by the\\nturning of the patient s eyes, by increasing or diminishing\\nthe distance between patient and surgeon or the distance\\nbetween the light and mirror, or the strength of the\\nlight. The amount of pigment in the eye-ground will\\nchange the general appearance of the reflex, being dim\\nin some mulattoes, and very light in the blonde or albino.\\nIf the refractive error is a high one, the reflex will appear\\ndull or if a low error, it will appear very bright. If the\\nmedia are not clear, the reflex will be altered accordingly.\\nThe bright pin-point catoptric images seen on the cornea\\nand lens are not parts of the test, and should be avoided or\\nignored. The 1 mm. bright ring of light sometimes seen\\nat the edge of the pupil should be avoided by the beginner\\nin retinoscopy, as it is an indication of spheric aberration,\\nwhich he will have to consider after mastering other details\\nof the method.\\nFacial Illumination. The rays of light reflected from\\nthe mirror illuminate a portion of the patient s face, and\\nalways move in the same direction as that in which the\\nmirror is tilted, no matter whether the mirror is plane or\\nconcave.\\nRetinal Illumination. This corresponds to the portion\\nof the retina which receives the rays of light reflected from\\nthe mirror. The retinal illumination is also called the\\nimage, the light area, etc.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0168.jp2"}, "169": {"fulltext": "RETINOSCOPY. l6l\\nThe Shadow. This is the non-illuminated portion of\\nthe retina immediately surrounding the illumination. The\\nillumination and shadow are, therefore, in contact if the\\nillumination changes its place upon the retina by a move-\\nment of the mirror, then the shadow will move also. By\\nthis change of illumination and shadow we speak of a\\nmovement of the shadow.\\nWhere to Look and What to Look for. Rotating the\\nmirror through the various meridians of the eye, the\\nobserver makes a note of the (i) form, (2) direction, and\\n(3) rate of movement of the retinal illumination as he\\nwatches for them through a four or five millimeter area at\\nthe apex of the cornea, as this is the portion of the refract-\\nive media in the normal eye that the patient will use\\nwhen the effects of the cycloplegic pass away and the\\npupil regains its normal size.\\nPoint of Reversal. To find the point of reversal is the\\nunderlying principle of retinoscopy. For example, having\\ndetermined with the plane mirror at a distance of one meter\\nthat the retinal illumination moves with the movement of the\\nmirror and a +2.50 S. stops all apparent movement (no\\nmovement of the illumination being seen and the shadow\\nhaving disappeared), the observer knows that his eye is at\\nthe point of reversal. Or with the concave mirror the\\nretinal illumination will move opposite to the movement of\\nthe mirror and will stop with -f~ 2 -50 S. before the eye.\\nThe point at which all movement of the retinal illumina-\\ntion appears to have ceased is the point of reversal.\\nThe real movement of the retinal illumination de-\\npends upon the mirror whether it is concave or plane.\\nWith the plane mirror the retinal illumination always moves\\nwith the mirror and the light on the face whereas with the\\nconcave mirror (focusing rays before they enter the eye),\\n14", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0169.jp2"}, "170": {"fulltext": "1 62 REFRACTION AND HOW TO REFRACT.\\nthe real movement of the retinal illumination is always\\nopposite to that of the mirror. The student should not\\nget the real and apparent movements confused, but pay\\nclose attention to the apparent movement.\\nDirection of the Apparent Movement of the Retinal\\nIllumination. With the plane mirror, the apparent move-\\nment of the retinal illumination will be with the mirror and\\nwith the light on the face as long as the observer is within\\nthe point of reversal but just as soon as the observer is\\nbeyond the point of reversal, the retinal illumination will\\nappear to move opposite to the movement of the mirror\\nand opposite to the movement of the facial illumination.\\nFig. 144.\\nWith the concave mirror the apparent movement of the\\nretinal illumination will be with the movement of the mir-\\nror and the light on the face as long as the observer is be-\\nyond the point of reversal (Fig. 142); but just as soon as\\nthe observer s eye is within the point of reversal, the retinal\\nillumination will appear to move against the movement of\\nthe mirror and against the light on the face. (See Fig. 143.)\\nRate of Movement of the Retinal Illumination. This\\nis influenced by several factors, but practice will teach the\\nobserver that when the retinal illumination appears to move\\nslowly, the refractive error is a high one, and when it moves\\nfast, the refractive error is a low one.\\nFigure 144 represents a myopic eye with its far point", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0170.jp2"}, "171": {"fulltext": "RETINOSCOPY.\\n63\\n(point of reversal) at R/, and when rotating the mirror, this\\npoint moves to R r/ but if the eye had its far point at F\\nand the mirror was rotated to F r/ then the illumination at\\nR having to move through a smaller arc in the same time,\\nappears to move slowly as compared with F r which ap-\\npeared to move fast. The same condition is shown in\\nfigure 145, in which the observer appears to see an erect\\nvirtual image back of the retina, and R r appears to move\\nslowly as compared with F which appears to move fast.\\nForm of Illumination. A large, round illumination\\nmay signify emmetropia, hyperopia, or myopia, with or with-\\nout astigmatism in combination. Astigmatism is recognized\\nFig. 145.\\nby the presence of a band of light, and this band of light\\nmay be seen before any correcting lens has been placed be-\\nfore the eye if the astigmatic error is high or it will be\\nrecognized during the process of neutralization if the error\\nis small i. e., if the astigmatism is of low degree. The pres-\\nence of astigmatism is known, therefore, by the band of light\\nor when the illumination appears to move faster in one\\nmeridian than in the meridian at a right angle. The astig-\\nmatism is in the meridian of slow movement.\\nThe apparent difference between the plane and con-\\ncave mirror in the direction of movement of the retinal\\nillumination. With the plane mirror the rays of light are\\nreflected as if they came from a point just as far back of", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0171.jp2"}, "172": {"fulltext": "164 REFRACTION AND HOW TO REFRACT.\\nthe mirror as the original source of light is in front of it.\\nThe surgeon s eye behind a plane mirror is, therefore, in\\nthe path of these rays, and sees that portion of the pupil-\\nlary area illuminated to which these rays are directed.\\n(See Fig. 146.)\\nWith the concave mirror the reflected rays come to a\\nfocus, forming an inverted image of the flame, which be-\\ncomes the immediate source of light in front of the\\nobserver s eye. When the concave mirror is tilted, the\\nimmediate source of light goes in the same direction, but\\nwith the result that the opposite portion of the pupillary\\narea is illuminated. (See Fig. 143.) This shows the\\nFig. 146.\\nimmediate source of light at \\\\J and mirror tilted downward\\nthe rays proceeding from \\\\J diverge and illuminate the\\nupper portion of the pupillary area. Tilting the mirror\\nupward, the immediate source of light at \\\\J moves upward\\nalso (L 2 and the lower portion of the pupillary area be-\\ncomes illuminated. (See also Fig. 142.)\\nRule for Neutralizing Lenses with the Plane Mirror.\\nWhen the retinal illumination appears to move in the\\nsame direction as that of the mirror, the observer is within\\nthe point of reversal and a plus lens must be placed before\\nthe eye to stop all apparent movement. When the retinal\\nillumination appears to move in the opposite direction to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0172.jp2"}, "173": {"fulltext": "RETINOSCOPY. 1 65\\nthat in which the mirror is tilted, the observer is beyond\\nthe point of reversal, and a minus lens must be placed\\nbefore the eye to stop all apparent movement.\\nRule for Neutralizing Lenses with the Concave\\nMirror. When the retinal illumination appears to move in\\nthe same direction as that in which the mirror is tilted, the\\nobserver is beyond the point of reversal, and a minus lens\\nmust be placed before the eye to stop all apparent move-\\nment. When the retinal illumination appears to move in\\nthe opposite direction to that in which the mirror is tilted,\\nthe observer is within the point of reversal, and a plus lens\\nmust be placed before the eye to stop all apparent move-\\nment.\\nRule for neutralizing lenses, no matter whether the\\nmirror is plane or concave. When within the point of\\nreversal, use a plus lens, and when beyond the point of\\nreversal, use a minus lens.\\nApplication of Retinoscopy in Emmetropia (Fig.\\n146). Rays of light proceed parallel from an emmetropic\\neye under the influence of a cycloplegic, and if a 1 S.\\nis placed in front of such an eye, the rays will converge\\nand form a point of reversal at I meter distance, and the\\nobserver at this point will not be able to see any move-\\nment of the retinal illumination. The. same result would\\nhave been obtained at of a meter if a -j-3 S. had been\\nused, or at 4 meters if a +0.25 S., or at y 2 of a meter\\nif a +2 S. had been used, etc.\\nIn taking the patient from the dark-room to test his\\nvision at 6 meters, an allowance must always be made for\\nthe distance from the patient s eye at which the point of\\nreversal was found. If at J^ of a meter, 3 S. must be de-\\nducted from the lens used if at y^ of a meter, 4 S.; if at\\n6 meters, nothing, or o. 1 2.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0173.jp2"}, "174": {"fulltext": "1 66 REFRACTION AND HOW TO REFRACT.\\nApplication of Retinoscopy in Hyperopia. The\\nsame conditions hold good in hyperopia as in emmetropia.\\nIf a +4 S. gives a point of reversal at one meter, then\\nI S. must be taken from the 4 S. to give the eye parallel\\nrays of light, or infinity vision. If a -[-4 S. gave a point\\nof reversal at 2 meters, then 0.50, S. would have to be\\ndeducted from the 4 S. for the infinity correction, which\\nwould be +3.50 S.\\nApplication of Retinoscopy in Myopia. Rays of light\\nfrom a myopic eye come to a focus at some point inside of\\ninfinity, and if the surgeon so desires, he may approach such\\nan eye from a distance of six meters, until he finds a point\\nwhere the retinal illumination ceases to move (where it does\\nnot appear to move) and then, measuring this distance from\\nthe eye under examination, he can quickly calculate the\\namount of the myopia. This can not be done with the\\nconcave mirror if the myopia is more than 2 S. If the\\nreversal point is at 4 meters, 3 meters, 2 meters, 1 meter,\\ny 2 of a meter, of a meter, or y^ of a meter, then the\\nmyopia would be 0.25 S., 0.33 S., 0.50 S., 1 S., 2 S., 3 S.,\\n4 S., respectively.\\nIf the surgeon will always refract the patient s eyes so\\nthat he gets the point of reversal at 1 meter distance, he\\nwill have the following rule to guide him i. c.\\nTo add a 1 sphere to the dark-room correction, no\\nmatter what that may be. For example\\nDark-room, o.oo -I-0.25S. -(-0.50S. -(-0.75s. +1.00S. +1.25 S.\\nAdd, 1.00S. 1.00S. 1.00S. 1.00S. 1.00S. 1.00S.\\nInfinity, i.ooD. 0.75D. 0.50D. 0.25 D. 0.00 +0.25 D.\\nApplication of Retinoscopy in Astigmatism. If the\\nsurgeon has mastered retinoscopy in hyperopia and myopia,\\nhe should not have any difficulty in pursuing exactly the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0174.jp2"}, "175": {"fulltext": "RETINOSCOPY. 1 67\\nsame course in cases of astigmatism. As already stated,\\nthe presence of astigmatism is diagnosed by the presence\\nof a band or ribbon-like streak of bright illumination which\\nextends across the pupillary area.\\n(See Fig. 147.) This band of light\\nmay be seen before any neutralizing\\nlens is placed in front of the eye,\\nif the astigmatism is in excess of\\nthe spheric correction, as in the\\nfollowing formula\\n+0.75 sph. C+4-50 cyl. axis 105 degrees. FlG H7-\u00e2\u0080\u0094 Band of Light.\\nX r j Astigmatism Axis 90 de-\\n1. 00 sph. Z2 5- 00 cyl. axis 165 degrees. n-r^^l\\ngrees.\\nOr the presence of astigmatism\\nmay not be recognized until after a sphere has been placed\\nin front of the eye, as in one of the following formulas\\n-I-4.50 sph. 3 +\u00c2\u00b0-75 c yl- ax is 75 degrees.\\n5.00 sph. 3 1. 00 cyl. axis 180 degrees.\\nIn refracting cases of astigmatism with the retinoscope,\\nall the surgeon has to do is to refract the meridian of least\\nametropia first, and then the meridian of greatest ametropia.\\nTaking the following formula\\n-I-2.50 sph. 3 -(-i.oo cyl. axis 90 degrees\\nin the dark-room a +3.50 S. would make all movement\\ncease in the vertical meridian, at one meter distant but\\nwhen the mirror is tilted in the horizontal meridian, there\\nwould be seen a band of light extending across the pupil\\non axis 90 degrees. Then, substituting +4-50 S. for the\\n3.50 S., all movement will cease in the horizontal meridian,\\na +4.50 S. neutralizing the horizontal meridian. The\\ndifference between these two spheres is 1 D., which is the\\namount of the astigmatism. In neutralizing astigmatism\\nthe writer advises using spheres, and after each meridian", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0175.jp2"}, "176": {"fulltext": "1 68 REFRACTION AND HOW TO REFRACT.\\nhas been refracted, to make the cylindric correction, and\\nprove it, if so desired.\\nAxonometer. To find the exact axis subtended by the\\nband of light while studying the retinal illumination, when\\nthe meridian of least ametropia has been corrected, the\\nwriter has suggested a small instrument, which, for want of\\na better name, he has called an axonometer. This is a\\nblack metal disc, with a milled edge, I y 2 mm. in thickness,\\nof the diameter of the ordinary trial-lens, and mounted in\\na cell of the trial-set. It has a central round opening, 1 2\\nFig. 148.\\nmm. in diameter the diameter of the average cornea at its\\nbase. Two heavy white lines, one on each side, pass from\\nthe circumference across to the central opening, bisecting\\nthe disc. To use the axonometer, place it in the front\\nopening of the trial -frame, and with the patient seated erect\\nand frame accurately adjusted, so that the cornea of the eye\\nto be refracted occupies the central opening. As soon as\\nthat lens is found which corrects the meridian of least\\nametropia, and the band of light appears distinct, turn the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0176.jp2"}, "177": {"fulltext": "RETINOSCOPY. 1 69\\naxonometer slowly until the two heavy white lines accu-\\nrately coincide, or appear to make one continuous line with\\nthe band of light. (See Fig. 148.)\\nThe degree mark on the trial -frame to which the arrow-\\nhead at the end of the white line then points is the exact\\naxis for the cylinder.\\nApplication of Retinoscopy in Mixed Astigmatism.\\nHere the dark-room result (after making deductions for\\nthe distance of the point of reversal) will show one meridian\\nmyopic and the other, at right angles to it, as hyperopic. If\\nthe astigmatism is more than one diopter in each meridian,\\nthe surgeon will diagnose in the dark-room the condition\\nof mixed astigmatism by opposite movements in the me-\\nridians of minimum and maximum ametropia.\\nApplication in Irregular Astigmatism. This condi-\\ntion is either in the lens or cornea, usually in the latter.\\nThe reflex is more or less obscured by areas of darkness,\\nwhich make it extremely difficult to study the refraction,\\nand the observer will have to change his distance repeat-\\nedly to find clear spaces as close to the center of the pupil\\nas possible, as it is this portion of the pupillary area that\\nthe patient will see through when the mydriatic effect passes\\naway. The kaleidoscopic picture obtained by moving the\\nmirror so as to describe a circle at the periphery of the\\npupillary space is quite diagnostic of the corneal condition.\\nWhatever result is obtained should be kept for reference in\\na postcycloplegic manifest refraction, as it will not always\\ndo to order the glasses while the eye has its pupil dilated.\\nThe patient may choose a slightly different correction in\\nsuch cases, after the pupil regains its accustomed size.\\nIrregular Lenticular Astigmatism. This is often\\nmore uniform than the corneal variety, and is characterized\\nby faint striae in the lens, pointing in toward the center. If\\n15", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0177.jp2"}, "178": {"fulltext": "170\\nREFRACTION AND HOW TO REFRACT.\\nthe striae are not very faint, they may be recognized with the\\nophthalmoscope, even before any cycloplegic has been used.\\nScissor Movement (see Fig. 149). This is a condi-\\ntion in which two bands of light are present, usually in\\nthe horizontal meridian or inclined a few degrees therefrom.\\nTilting the mirror in the vertical meridian, a band of light\\nis seen to come from above and to meet another band, which\\ncomes from below while these two bands are approaching,\\nthe dark space between them gradually disappears, until the\\ntwo bands unite and form one band\\nacross the pupil in or approximat-\\ning the horizontal meridian. This\\nmovement of the bands is likened\\nto the action of the blades of a pair\\nof scissors, and hence the name.\\nTo refract a case of this character,\\nthe observer must proceed slowly\\nand endeavor to neutralize the\\nhorizontal meridian first, and then\\nadd minus cylinders with the axis corresponding to the\\naxis of the two bands. The resulting prescription should\\nalso be a plus sphere with a minus cylinder, the cylinder\\nof less strength than the sphere, as the condition is not one\\nof mixed astigmatism, the patient preferring this combina-\\ntion, as a rule.\\nConic Cornea. In this condition the observer is im-\\npressed at once with the bright central illumination, which\\nusually moves opposite to the movement of the peripheral\\nillumination. The best way to neutralize a case of this\\ncharacter is to proceed as in a case of irregular astigmatism.\\nThe observer should also be on the lookout for a band of\\nlight in this central illumination, as most of these cases are\\nastigmatic.\\nFig. 149. Scissor Move\\nmerit.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0178.jp2"}, "179": {"fulltext": "RETINOSCOPY.\\n171\\nSpheric Aberration. This is of two kinds positive and\\nnegative. (See Figs. 150 and 151.) In the positive form\\nthe peripheral refraction (A, A, that at the edge of the\\npupil) is stronger than the central (B, B) the reverse of\\nFig. 150. Positive Aberration.\\nFig. 151. Negative Aberration.\\nthis condition, negative aberration, is seen in conic cornea.\\nThese two varieties of refraction should not worry the\\nobserver, as most of the peripheral aberration is covered\\nup by the iris when mydriasis passes away, and, therefore,\\nis not of any great moment, except in conic cornea.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0179.jp2"}, "180": {"fulltext": "CHAPTER VII.\\nMUSCLES.\\nExamination of the External Eye Muscles.\\nGeneral Considerations. When the retinal image of an\\nobject is situated exactly on the fovea, the eye is said to\\nfix the object.\\nNormally, when both eyes fix the object, each eye\\nhas an image of the object on its fovea, and these foveal\\nimages or impressions are transmitted to the brain and fused\\nas one image in the visual centers. This condition is spoken\\nof as equipoise, or orthophoria, and the eyes are said to be\\nin equilibrium, or to balance. Whenever one eye alone fixes\\nan object, and the fellow-eye receives the image of the same\\nobject on a part of its retina distant from the fovea, then\\nthe brain takes note of two separate impressions, and this\\ncondition is spoken of as double vision (diplopia).\\n(a) The image of an object formed upon the retina above\\nthe fovea is projected downward i. e., objects situated\\nbelow the horizontal line of vision are recognized by that\\nportion of the retina above the fovea.\\n(b) The image of an object formed upon the retina below\\nthe fovea is projected upward i. e. t objects situated above\\nthe horizontal line of vision are recognized by that portion\\nof the retina below the fovea.\\n(c) The image of an object formed on the retina to the\\nnasal side of the fovea is projected toward the temporal\\nside i. c, objects to the temporal side have their images\\nformed upon the nasal portion of the retina.\\n172", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0180.jp2"}, "181": {"fulltext": "MUSCLES.\\n173\\n(d) The image of an object formed on the retina to the\\ntemporal side of the fovea is projected toward the nasal side\\n\u00e2\u0080\u0094i. e.\\\\ objects to the nasal side have their images formed\\nupon the temporal portion of the retina.\\nHomonymous Diplopia (Greek, 6fjd vufio from 6;j.6q,\\nsame, and ovupa, name). Figure 152 shows the right\\nFig. 152.\\neye (R) fixing upon the object (O), but the left eye is\\nturned inward, so that rays from O fall upon its retina to the\\nnasal side of the fovea (M), and are projected outward to\\nthe temporal side the result is that the left eye sees a false\\nobject to the left of the real object. This condition of the\\nobjects is spoken of as homonymous diplopia.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0181.jp2"}, "182": {"fulltext": "174\\nREFRACTION AND HOW TO REFRACT.\\nHeteronymous Diplopia (Greek, erspo^, other and foufia,\\nname). Figure 153 shows the right eye fixing the object\\n(O), but the left eye is turned outward, so that rays from O\\nfall upon the retina to the temporal side of the fovea and are\\nprojected to the nasal side, with the result that the left\\neye sees a false object\\nto the right of the real\\nobject. This condi-\\ntion of the objects is\\nspoken of as heter-\\nonymous or crossed\\ndiplopia.\\nHyperphoria\\n(Greek, v-ep, over,\\nabove 4 \u00c2\u00b0P a t m\\ntion). In the con-\\nsideration of vertical\\ndiplopia, which is\\nalways a condition\\nof crossed diplopia,\\nnever homonymous\\ndiplopia, the eye\\nwhich is deviated up-\\nward is spoken of as\\nthe hyperphoric eye,\\nand necessarily its\\nimage must be lower\\nthan its fellow. For instance, if the left eye fixes an object\\nand the right eye is turned upward, the rays of light from\\nthe object would fall upon the upper part of the retina of the\\nright eye, and would be projected downward below the true\\nobject and this position of the right eye is spoken of as\\nright hyperphoria. Or if the right eye fixes an object and\\nO M\\nFig. 153.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0182.jp2"}, "183": {"fulltext": "MUSCLES. 175\\nthe left eye sees a false object below, then the position of\\nthe left eye is spoken of as left hyperphoria. Unfortunately,\\nin hyperphoria (unless from paralysis) the position of the\\neyes does not tell whether the right superior rectus is too\\nstrong and the left inferior rectus too weak, or the left supe-\\nrior rectus too weak and the right inferior rectus too strong.\\nMuscle Phorometry. Testing the power of the ocular\\nmuscles.\\nAbduction. The power of the external recti muscles to\\nturn the eyes outward. The patient is comfortably seated\\nand told to look at a point of steady light at a distance of\\nabout 6 meters, slightly below the level of his eyes, never\\nabove the level. In this position prisms with their bases in-\\nward are placed in front of one or both eyes until the\\npatient says he sees two lights very close together. The\\nstrength of the prism or prisms thus placed before the\\neyes which will just permit the eyes to see one object\\nand if increased would produce diplopia, represents the\\npower of the external recti muscles. This is spoken of as\\nthe power of abduction, and is abbreviated Abb. For\\nexample, if with 7 centrads, base in, before the eyes there\\nare two lights, and with 6 centrads there is only one light,\\nthen 6 centrads would represent the amount of the abduc-\\ntion. In other words, in the case supposed, as long as\\nthere is less than 7 centrads before the eyes, base inward,\\nthe external recti muscles can overcome their effect, but as\\nsoon as a prism stronger than 6 centrads is used, then the\\nexternal recti muscles can not counteract the effect, and\\ndiplopia is the result.\\nAdduction. The power of the internal recti muscles to\\nturn the eyes inward. The power of the internal recti is\\ntested in the same way as the external, except that the\\nprism is placed base outward. This is spoken of as adduc-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0183.jp2"}, "184": {"fulltext": "I76 REFRACTION AND HOW TO REFRACT.\\ntion, and is abbreviated Add. For example, if with 19\\ncentrads, base out, before the eyes two lights are seen, and\\nwith 1 8 centrads only one light, then 1 8 centrads represent\\nthe power of adduction. In other words, as long as there is\\na prism of 1 8 or less than 1 8 centrads before the eyes, base\\noutward in this case, the internal recti muscles can over-\\ncome the effect but as soon as a prism stronger than 1 8\\ncentrads is used, then the internal recti muscles can not\\ncounteract the effect, and diplopia is the result. It must\\nbe remembered that the internal and external recti are\\nantagonistic, and that the muscles of the two eyes are\\ntested together. The relative power of adduction to abduc-\\ntion has been variously estimated, but most authorities are\\nagreed that adduction is about three times that of abduc-\\ntion, or about 3 to 1 that is to say, in eyes with normal\\nmuscle balance, if adduction is represented by 18 centrads,\\nthen abduction should be 6 or if adduction is represented\\nby 24 centrads, then abduction should be 8 centrads or if\\nadduction is 12 centrads, then abduction should be 4 cen-\\ntrads, etc.\\nSursumduction. This is the power of the eyes to fuse\\ntwo images when one eye has a prism placed base up or\\ndown before it. For example, if a 3^ centrad prism is\\nplaced base up or down before either eye and diplopia\\nresults and persists, and then a 3 centrad is substituted and\\nthere is no diplopia, then the eyes have overcome the effect\\nof the prism and the amount of the sursumduction is said\\nto be 3 centrads. This test for sursumduction is made at\\nthe same distance as in testing the lateral muscles. In\\nhealth the power of the superior and inferior recti muscles\\nis, as a rule, the same that is to say, they antagonize each\\nother equally. The power of the superior recti is spoken of\\nas supraduction and that of the inferior recti, as infraduction.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0184.jp2"}, "185": {"fulltext": "MUSCLES. 177\\nMuscular Imbalance. Whenever there is any disturb-\\nance in the power, strength, or force of the ocular muscles,\\nthe condition is no longer one of equipoise, or equilibrium,\\nor muscle balance, but is spoken of as muscular imbalance\\n(heterophoria). From this statement it must not be sup-\\nposed that the two eyes can not simultaneously fix an\\nobject, any more than it must be supposed that a hyperopic\\neye can not see or have vision without correcting\\nglasses.\\nJust as in hyperopia distant vision may be made clear\\nby the effort of accommodation, so in muscular imbalance\\nthe visual axes can be directed to one point of fixation by\\nincreased innervation. Muscular imbalance is subdivided\\ninto two classes insufficiency and strabismus.\\nThe following nomenclature of muscular anomalies, sug-\\ngested by Stevens, of New York, is in common use\\nOrthophoria, perfect muscle balance, equipoise, or binocular\\nequilibrium.\\nOrthotropia, perfect binocular fixation.\\nHeterophoria, imperfect binocular balance, or imperfect bin-\\nocular equilibrium.\\nHeterotopia, a squint or decided deviation or turning from\\nparallelism.\\nHyperphoria, a tendency of one eye to deviate upward.\\nHypcrtropia, a deviation of one eye upward.\\nEsoplwria, a tendency of the visual axes to deviate inward.\\nEsotropia, a deviation of the visual axes inward.\\nExopJwria, a tendency of the visual axes to deviate outward.\\nExotropia, a deviation of the visual axes outward.\\nHypcresophoria, a tendency of the visual axis of one eye\\nto deviate upward and inward.\\nHypercsotropia, a deviation of the visual axis of one eye\\nupward and inward.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0185.jp2"}, "186": {"fulltext": "I78 REFRACTION AND HOW TO REFRACT.\\nHyper exophoria, a tendency of the visual axis of one eye\\nto deviate upward and outward.\\nHyperexotropia, a deviation, of the visual axis of one eye\\nupward and outward.\\nInsufficiency. Also called latent deviation, hetero-\\nphoria, or latent squint. This may be defined as the con-\\ndition in which there is a tending or tendency of the visual\\naxes to deviate from the point of fixation this may be slight\\nor transitory.\\nCauses of Insufficiency. The chief cause of insuffi-\\nciency is some form of ametropia. Another cause may be\\nan anatomic defect of one or more of the ocular muscles\\nthemselves, or a weakness of the muscle or muscles indi-\\nvidually, or as a result of some systemic weakness. The\\nocular muscles often sympathize with the economy.\\nSymptoms of Insufficiency, or Muscular Asthenopia.\\nAccommodative and muscular asthenopia are intimately\\nassociated, and the latter is so often the companion of the\\nformer that they produce symptoms which are identical in\\nboth and make it difficult to draw any sharp line of demar-\\ncation between the two. In muscular asthenopia, how-\\never, the patient complains that the eyes become weak\\nor tired after any prolonged use, and that this is espe-\\ncially apt to occur by artificial light that nearby\\nobjects (reading, writing, or sewing) grow dim that the\\nwords seem to jump, of the letters run together, and\\nin some cases occasionally, and in others more frequently,\\nobjects appear double for a moment. Sometimes one of\\nthe eyes feels as if it was turning outward or inward.\\nThefe are innumerable reflex symptoms, dizziness, nausea,\\nvomiting, fainting, and, in some instances, all becomes\\ndark for a minute. Such patients often become very\\nanxious, fearing sudden blindness, etc.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0186.jp2"}, "187": {"fulltext": "MUSCLES. 1 79\\nDiagnosis or Tests for Insufficiency (Heterophoria).\\nBefore taking up the individual tests for insufficiencies, it is\\nwell for the observer to study the movements or excursions\\nof the eyes and to do this the patient, with his head erect\\nand steady in one position, fixes with his eyes the point of\\na pencil held in the hand of the observer at about thirteen\\ninches distant. The pencil is moved from left to right and\\nfrom right to left, and upward and downward as this is\\ndone, the surgeon should watch closely to see that each\\neye has a normal mobility and the two eyes move together.\\nFrom a central point of fixation the eyes should move\\ninward about 45 degrees, outward 45 or 50 degrees,\\nupward about 40 degrees, and downward about 60 degrees.\\nThe tropometer of Stevens will estimate the limit of motion\\nof each eye separately, but if there is a defect in mobility,\\nthe surgeon may recognize it by comparing the distance of\\nthe corneal edge in each eye from a certain definite fixed\\npoint for instance, whether the lid margins encroach\\nequally upon the cornea or have equal intervals between\\ncornea and lid edges.\\nThe Cover Test. The patient is told to look at the\\npoint of a pencil held in the hand of the surgeon on a level\\nwith the patient s eyes in the median line, and distant about\\neighteen inches, or at an object six meters distant. While\\nthe eyes fix the point of the pencil or distant object, the\\nsurgeon covers one eye with a small card, and a moment\\nlater quickly withdraws it and observes the position and\\nmovement of the eye which he has just uncovered if it\\nmoved inward toward the nose to fix the point of the pen-\\ncil, then there must have been an outward tendency of that\\neye when under cover in other words, the external muscles\\nmust have been strong or the internal weak. If the eye\\nthus released from the cover had moved outward toward", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0187.jp2"}, "188": {"fulltext": "l8o REFRACTION AND HOW TO REFRACT.\\nthe temple to fix the point of the pencil, then the external\\nrecti must have been weak or the internal strong. If the\\neye released from cover goes up to fix. then the fellow-eye\\ndeviates upward, and vice versa. This test is not always\\nreliable, and yet it may be a guide to further study.\\nThe Fixation Test. Instead of covering one eye, as in\\nthe previous test, the patient fixes the point of the pencil\\nas it is slowly advanced in the median line toward the nose,\\nup to within four inches, if necessary. During this advance\\nof the pencil, if there is a weakness of the interni, the eye\\nwith the weaker internus is the one which will usually\\ndeviate outward.\\nTo Determine Lateral Insufficiency. The condition\\nin which there is either a tendency for the visual axes to\\ndeviate outward (exophoria), or a tendency for the visual\\naxes to deviate inward (esophoria). Proceed by producing\\nvertical diplopia. Place a ten centrad prism base down\\nbefore one eye, for instance, the right eye, and have the\\npatient look at a point of light on a level with his eyes at a\\ndistance of six meters. He will see two lights, one above\\nthe other the upper light must belong to the right eye,\\nbecause the prism before the right eye bent the rays down-\\nward. If one light is directly above the other, then the\\ncondition is presumably one of equilibrium or equipoise.\\nIf the upper light, however, is to the right, then the\\nvisual axes deviate inward (esophoria). The amount of\\nthe esophoria (insufficiency of the external recti) is repre-\\nsented by that prism placed base outward before the left\\neye which will bring one light directly above the other. If\\nthe upper light had been to the left, then there would have\\nbeen a tendency of the visual axes outward (exophoria,\\ninsufficiency of the internal recti), and the amount of the\\nexophoria is represented by the strength of prism placed", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0188.jp2"}, "189": {"fulltext": "MUSCLES. 15 1\\nbase inward which will bring one light directly above the\\nother.\\nTo Determine Vertical Insufficiency (Hyperphoria).\\nProceed by producing lateral diplopia. Place a ten centrad\\nprism base inward before the right eye, and have the patient\\nlook at a point of light, as in testing for lateral insufficiency.\\n(It is always well to have the point of light just in front of\\na large piece of black felt cloth tacked upon the wall.)\\nIf the two lights which the patient sees are on a horizontal\\nline, then the condition is presumably one of equipoise. But\\nif the right light is lower than the left, there is a tendency\\nof the visual axis of the right eye to be higher than its\\nfellow. As to which muscle is at fault, this test will not\\ntell, and Stevens tropometer will have to be used. The\\namount of the deviation is represented by the strength of\\nprism placed base down before the right, or upward before\\nthe left eye which will bring the two lights into a horizontal\\nline i. c, on a level.\\nTo Determine Lateral Insufficiency at the Reading\\nDistance. Have the patient look at a black dot, with a\\nblack line two or three inches long running perpendicularly\\nthrough it, at a distance of about thirteen inches. This is\\nknown as the line-and-dot test of von Graefe, and on a\\nlarger scale may also be used in the previous tests. A prism\\nof seven or eight centrads is placed, with its base down, in\\nfront of the right eye. If the patient sees two dots exactly\\none above the other on one line, there is not supposed to be\\nany insufficiency. If, however, there are two lines and\\ntwo dots, and the upper dot is on the right, there is in-\\nsufficiency of the externi (esophoria) for near. The amount\\nof the insufficiency is represented by the strength of prism,\\nplaced base outward, before the left eye which will bring\\nthe two dots exactly on one line. If the upper dot is to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0189.jp2"}, "190": {"fulltext": "182\\nREFRACTION AND HOW TO REFRACT.\\nthe left, then there is insufficiency of the interni (exophoria)\\nfor near, and the amount of the insufficiency is represented\\nby the strength of prism placed base inward over the left\\neye which will bring the two dots, one above the other, on\\none line.\\nThese tests for insufficiencies should always be made be-\\nfore estimating the refraction, and also after the correcting\\nlenses are carefully placed, with their optic centers, before\\nthe eyes.\\nTo avoid confusion in making these tests, when a point\\nof light is used as the fixing object, it is customary to place\\nFig. 154.\u00e2\u0080\u0094 Maddox Rod.\\nFig. 155.\\na piece of plane dark red glass before one eye, so that the\\nred light always corresponds to the eye with the red glass.\\nOr a Maddox rod (Fig. 1 54), white or red, may be used\\nfor the same purpose. This may be a series of rods (see\\nFig. 155) placed in a metal cell of the trial-case, and the\\neye, looking through it at the light, will see the image of\\nthe flame distorted into a streak of broken light. A strong\\ncylinder from the trial-case will answer the same pur-\\npose. As the rod refracts rays of light opposite to its axis,\\nthe eye will see a streak of light in the reverse meridian to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0190.jp2"}, "191": {"fulltext": "MUSCLES. 183\\nthat in which its axis is placed. To expedite the deter-\\nminations, the rotary prism of Cretes or the revolving\\nprisms of Risley may be employed. This latter apparatus\\n(see Fig. 156) is composed of\\ntwo superimposed prisms of 1 5\\ncentrads each, and mounted in a\\nmilled-edged cell of the size of\\nthe trial-lens. By means of a\\nmilled-edged screw these prisms\\nare made to revolve so that in\\nthe position of zero they neutral-\\nize each other, and when rotated\\nover each other the prism FlG is6\\nstrength gradually increases un-\\ntil the bases of the prisms come together and equal 30\\ncentrads. The strength of the prism employed is indicated\\nby an index on the periphery of the cell.\\nStevens Phorometer. This is a very convenient appa-\\nratus, composed of two 4-degree prisms placed in a frame\\n3 y 2 inches from the eyes, which with an attached lever can\\nbe rotated so as to test the strength of the vertical and\\nlateral muscles. Indexes and letters at the periphery of\\nthe frame record the character and degree of the insuffi-\\nciency. (See Fig. 157.)\\nTreatment of, Insufficiencies. As ametropia is the\\nmost common cause of insufficiency, the first consideration\\nmust be to select the proper correcting glasses. After this\\nhas been accomplished, if the insufficiency still persists and\\nthe patient is not comfortable, then the muscles should re-\\nceive careful attention, and their condition be studied from\\nevery point of view. The patient s general health should\\nbe looked after, and if at all defective, must have remedies\\nprescribed for its improvement. In some instances the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0191.jp2"}, "192": {"fulltext": "1 84\\nREFRACTION AND HOW TO REFRACT.\\npatient may have to give up any close application of the\\neyes for a time and pursue an out-door life. Operative\\ninterference (tenotomy) must not be entertained until all\\nknown means for the relief of the muscular asthenopia\\nhave been exhausted.\\nThe prescribing of prisms, as a fixed rule, for permanent\\nuse, which correct insufficiency, except in vertical errors, is\\noften a serious mistake on the part of the surgeon, as in\\nmost instances they often do more harm than good by in-\\ncreasing the difficulty. Internally, sedatives will frequently\\nRevolving\\nMaddox Rod\\nPhorometer\\nRevolving\\nTrial Frame\\nRevolving\\nRotary Prism\\nFig. 157.\\ngive great satisfaction and permanent relief. The writer is\\npartial to the use of bromids with small doses of the iodid\\nof potash three or four times a day. The modus operandi\\nis not clear. The only guide that can be suggested is to\\nuse sedative treatment and rest of the eyes whenever there\\nis a congestion of the choroid and retina and when the\\nophthalmoscope shows the nerve edges hazy, the retina\\nwoolly, etc. In another class of patients the internal use\\nof nux vomica is the treatment par excellence, and it acts\\nbest in those cases where the nerve edges and the eye-\\nground in general appear clear and free from irritation.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0192.jp2"}, "193": {"fulltext": "MUSCLES. 185\\nTo use nux vomica it must be given in the form of the\\ntincture and increased, one drop at each dose, until the\\npatient becomes quite tolerant of it, taking as high as thirty,\\nforty, or even fifty drops three times a day, and then the\\ndose is gradually diminished. Nux vomica does not seem\\nto do well in cases in which the bromids are indicated as\\nabove, and vice versa. (De Schweinitz.)\\nTreatment of Insufficiency of the Internal Recti.\\nBecause the tests for heterophoria at 6 meters show an\\nability on the part of the patient to maintain equilibrium, it\\nmust not be supposed that there may not be an insufficiency.\\nThe normal ratio of adduction to abduction should be taken\\ninto consideration in every instance before coming to any\\nsuch conclusion.\\nAfter the proper correcting glasses have been prescribed\\nand the patient s general health looked after, attention, if\\nnecessary, should be directed to strengthening the weak\\nmuscles and to do this they must be given a certain amount\\nof systematic exercise, known as ocular gymnastics. That\\nsuccess shall result from ocular gymnastics means perse-\\nverance on the part of the patient and the exercises system-\\natically executed. There are two methods of procedure in\\ncases of exophoria Dr. George M. Gould, Med. News,\\nNov. 18, 1893\\n1. Have the patient fix the point of a pencil, or the\\nend of his finger held at arm s length, and slowly draw\\nit toward the bridge of the nose. If diplopia results while\\ndoing this, the exercise should cease, and be repeated from\\nthe original distance. This is a very convenient exercise\\nand should be practised several times a day and a number\\nof times at each sitting.\\n2. Prism Exercises. The patient is placed, standing,\\nabout a foot or two from a point of steady light, on a level\\nor slightly below the level of the eyes, and told to look at\\n16", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0193.jp2"}, "194": {"fulltext": "1 86 REFRACTION AND HOW TO REFRACT.\\nit, and at nothing else. In this position a pair of weak\\nprisms, bases out, in a trial-frame are placed in front of his\\neyes.\\nThen he is told to walk slowly backward as he keeps\\nhis eyes fixed on the point of light. Should diplopia de-\\nvelop at any distance short of 20 feet, then he is to raise\\nthe prisms, go back to his original position, and start over\\nagain. Repeating this a number of times in the surgeon s\\noffice, it will be found, in most instances, that at the first\\npractice a pair of 5 A or 10 A can be overcome at a distance\\nof 20 feet. When the distance of 20 feet from the light is\\nreached without developing diplopia, the patient is instructed\\nto slowly count 20 or 30 (keeping the light single during\\nthis time), then raise the prisms (gazing at the light), and to\\nslowly count 20 or 30 again. This exercise is repeated\\nthree or four times a day and a number of times at each\\npractice. A prescription is given for such a pair of square\\nprisms with a convenient frame to wear over the patient s\\nglasses. These exercises should, as a rule, be conducted\\nwith the patient wearing his correction. Instead of the\\nprism-frame, the patient may hold the square prisms with his\\nhands but these are tiresome to hold, and for general use\\nthe prism-frame, if not too heavy, is preferable. After a\\nfew days practice at home, the patient returns, and stronger\\nprisms which will permit the patient to maintain single\\nvision are ordered. This practice with stronger and stronger\\nprisms is repeated until the patient is able to overcome\\nprisms greatly in excess of the normal ratio of adduction\\nto abduction. It is often well to develop the power of the\\ninternal recti to three or four times the strength of the ex-\\nternal recti for when the exercises are stopped, some of the\\nstrength of adduction will rapidly disappear.\\nIt has been incidentally mentioned that prisms should", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0194.jp2"}, "195": {"fulltext": "MUSCLES. 187\\nnot be prescribed in combination with the ametropic cor-\\nrection for the treatment of insufficiency, and yet there is\\nan occasional exception to this statement in cases which\\nmust have prompt, though temporary, relief Occasion-\\nally, the relief may be permanent but this will not hap-\\npen very often. When ordering prisms for such a case, it\\nis best to prescribe them in the form of hook fronts, so that\\nthey may be thrown aside at any time. In hyperphoria the\\nfull prismatic correction (except in cases of presbyopia) is\\nseldom ordered, only about two-thirds of it, and this is\\ndivided between the two eyes base down before one, and\\nbase up before the other.\\nTreatment of Insufficiency of the Externi (Esophoria).\\nAs esophoria is a tendency of the visual axes to deviate in-\\nward, it will be found that patients with this form of insuffi-\\nciency suffer very little, if at all, when using the eyes at near\\nwork their chief discomfort arises from using the eyes for\\ndistant vision. The shopping headache, the opera head-\\nache, the train headache, may be due to this form of in-\\nsufficiency, but it is not so apt to cause discomfort if the\\nametropic correction is worn constantly. In other words, if a\\nhyperope does not wear his distance correction and accom-\\nmodates at the same time that he endeavors to maintain equi-\\npoise (relative hyperopia), he may at times suffer severely.\\nIf the symptoms of muscular asthenopia persist after pre-\\nscribing the ametropic correction, then prisms, bases out,\\nmay be prescribed as hook fronts to be worn over the con-\\nstant correction when using the eyes for distance. It has\\nbeen the writer s experience that esophoria of two, three,\\nor four degrees seldom gives the possessor any discomfort\\nwhatever. Prism exercises for esophoria give very little\\nbenefit, and are often a waste of time yet they should be\\ntried thoroughly if the case appears to demand it.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0195.jp2"}, "196": {"fulltext": "155 REFRACTION AND HOW TO REFRACT.\\nTreatment of the Insufficiency of the Superior and\\nInferior Recti. Having prescribed the ame tropic correc-\\ntion, an attempt should be made to strengthen the weak\\nmuscles by prism exercises prism base down before one\\neye, and base up before the other eye. While this does not\\noften give satisfactory results, yet it should be tried in each\\ninstance. If prism exercises do not correct the difficulty,\\nthen prisms which overcome most of the insufficiency should\\nbe prescribed for constant use. Failing in this second\\nattempt with prisms or with a full prismatic correction, then\\ntenotomy of the overacting muscle or muscles must have\\nconsideration.\\nTenotomy. As previously stated, tenotomy should\\nnever be resorted to until every other known means of relief\\nhas been tried, and even then no hard-and-fast rule can be\\ngiven for the amount of the insufficiency in degrees which\\nwill prompt such a procedure. Some patients with as\\nmuch as four or six degrees of esophoria may never suffer\\nthe least annoyance and yet other patients with the same\\namount will estimate their sufferings as almost beyond en-\\ndurance. And the same statement holds good in other\\nforms of insufficiency, especially exophoria. The question of\\npersonal equation, the patient s nervous system, hysteric\\ntendencies, etc., must all be considered before undertaking\\na tenotomy that may result in nothing but discourage-\\nment.\\nIf an operation has been deemed best, then it is for the\\nsurgeon to decide whether he will divide the tendon of the\\nstrong muscle or advance the weak muscle, or both. What-\\never operation or operations are performed, the amount of\\nthe deviation should be estimated immediately before, as well\\nas during and after, the operation. When a simple tenot-\\nomy is performed, the eye is usually left open (unband-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0196.jp2"}, "197": {"fulltext": "MUSCLES. ISO,\\naged) so that visual fixation is maintained, and the muscle\\nbalance tested frequently to see that, by subsequent con-\\ntraction, the insufficiency does not return. To avoid such a\\nmisfortune it may be necessary to use prism exercises dur-\\ning the healing process. The writer is not an advocate of\\npartial tenotomies.\\nStrabismus (a-pi fu to turn aside also called heter-\\notopia, cross-eye or squint, or manifest squint. This\\nis a condition of the eyes in which the amount of the\\ninsufficiency is so great that it can not (always) be over-\\ncome by muscular effort and, in fact, inspection often shows\\nthe manifest condition. Or strabismus may be defined as\\nthe condition in which the visual axis of one eye is deviated\\nfrom the point of fixation. The eye which has the image\\nof the object on its fovea is spoken of as the fixing eye,\\nwhile the other eye is termed the squinting or deviating\\neye. The squinting eye does not always have normal\\nvisual acuity and, in fact, correcting lenses will not\\nalways produce such a result.\\nVarieties of Strabismus. Convergent, divergent,\\nvertical, monolateral, alternating, periodic, concomitant,\\nand paralytic.\\nConvergent squint (con, together, and vergere, to\\nincline or approach also called internal squint (strabis-\\nmus convergens), esotropia. This is the condition in which\\nthe visual axis of one eye is deviated inward, the other\\nfixing the object or one eye fixing an object, the visual\\naxis of the other eye crosses that of the fixing eye closer\\nthan the object. (See Fig. 152.) This is the most common\\nform of squint. Both eyes have some form of hyperopia,\\nas a rule, the squinting eye usually being the most ame-\\ntropia The diplopia as a result of this condition is\\nhomonymous.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0197.jp2"}, "198": {"fulltext": "I9O REFRACTION AND HOW TO REFRACT.\\nDivergent squint (di, apart, and vergere, to in-\\ncline also called external squint (strabismus divergens),\\nexotropia. (See Fig. 153.) This is the condition in which\\nthe direction of the visual axis of one eye is directed out-\\nward, the other eye fixing the object or one eye fixing\\nan object, the visual axis of the other eye can cross it only\\nby being projected backward. The diverging eye is usually\\nmyopic.\\nMonolateral (one-sided) squint also called constant.\\nIt may be either convergent or divergent, but the squint is\\na constant condition of one eye.\\nAlternating Squint. This is the condition in which\\nat different times the right eye fixes and the left eye squints,\\nor the left eye fixes and the right eye squints. The vision\\nin one eye may be as good as that of its fellow.\\nPeriodic squint also called intermittent. This is the\\ncondition in which the visual axis of one eye occasionally\\ndeviates. It may eventually become constant, and is often\\nthe first indication of a beginning convergent or divergent\\nsquint.\\nVertical Squint. This is the condition in which the\\nvisual axis of one eye is deviated upward. Also called\\nhypertropia.\\nConcomitant Squint. This is the condition in which\\nthe squinting eye has freedom of movement and will follow\\nits fellow, and yet one eye deviates (inward or outward)\\nbecause of an inability to fix.\\nParalytic Squint. This is the opposite condition from\\nconcomitant, in which there is a restriction in the move-\\nment of one eye in a certain direction, due to a palsy of\\none or more of the muscles.\\nCauses of Squint. These are many and various. The\\nchief causes, however, are (1) Ametropia, which may pro-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0198.jp2"}, "199": {"fulltext": "MUSCLES. I9I\\nduce a change in the normal relationship between accom-\\nmodation and convergence (2) anatomic anomalies (3)\\nmechanic anomalies and (4) amblyopia.\\nI. Ametropia produces a change in the normal relation-\\nship between accommodation and convergence. While it is\\npossible for accommodation to take place without conver-\\ngence, or convergence without accommodation, yet there is\\nan affinity between the two processes which, if materially in-\\nterfered with, will produce diplopia and eventually squint. In\\nspeaking of relative hyperopia, it was shown that the accom-\\nmodative effort was accompanied by contraction of the inter-\\nnal recti muscles (convergence) so that in hyperopia of, say,\\nfour diopters, accommodating for infinity convergence would\\nbe stimulated to a proportionate degree at the same time\\nand if accommodating for a near point, the hyperope must\\naccommodate and converge just that much more. The\\nresult is that a person with a hyperopia of any considerable\\namount frequently squints inward in the effort to maintain\\nbinocular vision. If, now, one eye is more hyperopic than\\nthe other, the difficulty of adjusting convergence to accom-\\nmodation is increased. Say that the right eye has 3\\ndiopters and the left 4 diopters of hyperopia then the two\\neyes each exert 6 diopters to fix at 13 inches the left eye\\nstill has 1 diopter of its hyperopia remaining, and with the\\nresult that the retinal image of that eye is not clear, and\\naccommodation is still further taxed, stimulating at the\\nsame time the internal rectus, so that the left eye deviates\\ninward and ultimately remains convergent. This act of\\nconvergence explains the presence of convergent squint in\\nhyperopia, and also shows why the squinting eye usually\\nhas the higher refractive error. It must not be supposed\\nthat all hyperopic eyes have a squint, as some of these can", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0199.jp2"}, "200": {"fulltext": "192 REFRACTION AND H OW TO REFRACT.\\naccommodate without converging in a proportionate de-\\ngree, and this is especially so when the amount of the\\nhyperopia is the same in both eyes.\\nMyopic eyes, in contradistinction to hyperopic eyes, can\\nnot accommodate beyond their far points, but must con-\\nverge. If the myopia is 8 diopters, then these eyes would\\nhave to converge 8 meter angles to fix an object at that\\ndistance (5 inches) without any accommodative effort. It\\nmust also be borne in mind that myopic eyes are long eyes,\\nand that to converge 8 meter angles means a great effort\\non the part of the internal recti muscles, and this force can\\nnot be continued for any length of time without discomfort\\nthe result is, convergence is relaxed, and, one eye remaining\\nfixed, the other is turned outward. This is much more\\nlikely to happen if one eye is more myopic than the other.\\nThis explains the presence of divergent squint in cases of\\nmyopia. But it must not be supposed that all myopic eyes\\nnecessarily have squint, as some of them have roomy orbits,\\nstrong internal recti muscles, and a short interpupillary\\ndistance.\\n2. Anatomic Anomalies. This applies especially to the\\nbreadth of the face (skull) and the size of the eye and\\norbit. The broad face, which naturally gives a long inter-\\npupillary distance, predisposes to greater convergence than\\nthe narrow face. The long, myopic eye would not have\\nthe freedom of movement that the short eye possesses in\\nthe same-sized orbit.\\n3. Mechanic Anomalies. This refers especially to the\\nlength and strength of the extraocular muscles. Short\\nand strong internal recti would predispose to convergent\\nsquint, whereas strong external recti would develop diver-\\ngent squint.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0200.jp2"}, "201": {"fulltext": "MUSCLES. 193\\n4. Amblyopia. Statistics show that from thirty to\\nseventy per cent, of all squinting eyes are amblyopic. The\\ncause of the amblyopia may be that the eye was born\\ndefective in its seeing quality i. e., the cones at the fovea,\\nthe optic nerve, or the visual centers in the brain may be at\\nfault. Or if born perfect and having its visual axis deviated\\nby one of the many causes above mentioned, it may be-\\ncome amblyopic from not being used (amblyopia exanop-\\nsia). This consideration of cause and effect is most impor-\\ntant from a prognostic point of view.\\nAmong other causes of squint must be mentioned opaci-\\nties of the media, as nebula of the cornea, or any want of\\ntransparency in the cornea at or near the visual axis, or\\npolar or nuclear cataract. Temporary or intermittent\\nsquint may result from vitreous opacities, or from the rem-\\nnant of a hyaloid artery passing in front of the fovea. Parents\\noccasionally delude themselves with the idea that the\\nchild s squint is the result of whooping-cough, measles,\\nteething, sucking the thumb, or imitating a companion,\\netc., and are slow to believe that there can be any refrac-\\ntive error, forgetting that the supposed causes they men-\\ntion may be but coincidences.\\nTo Estimate the Amount of the Strabismus or\\nSquint. This is not always easy at the beginning of the\\nexamination, for the reason that the squinting eye has long\\nsince learned to ignore the false object and if the angle of\\nthe strabismus is large, the surgeon will have to reduce it in\\npart with a prism, so that the patient can see the false object\\nand if this is a point of light, a piece of dark red glass will\\nhave to be placed in front of the fixing eye. The strength\\nof the prism required to bring the two lights together will\\nbe the prismatic estimate of the deviation. Or the amount\\nof the squint may be roughly determined with the strabis-\\n17", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0201.jp2"}, "202": {"fulltext": "i 9 4\\nREFRACTION AND HOW TO REFRACT.\\nmometer. (See Fig. 158.) This is a piece of bone or ivory\\nhollowed on one side so as to fit the curve of the eyeball.\\nIts edge is graduated in millimeters. This device is held\\ngently against the lower lid of the squinting eye, so that\\nthe zero (o) mark corresponds to the center of the pupil as\\nthe eye fixes a distant object, the fellow-eye being under\\ncover. When the cover is removed,\\nthe squinting eye again deviates,\\nand the amount of the deviation is\\nagain noted by the position of the\\ncenter of the pupil of the squinting\\neye over the millimeter line on the\\ninstrument. Each millimeter of\\ndeviation is supposed to represent\\n5 degrees of deviation. This device\\nis not reliable, and is not in common\\nuse.\\nA more reliable estimate is ob-\\ntained by measuring the deviation\\non the arc of the perimeter. (See\\nFig. 159.) To do this, the patient\\nis seated with the squinting eye\\nopposite to the fixation point (R)\\nand instructed to look at a distant\\nobject (R) across the room, so that the object, the fixation\\npoint, and the squinting eye (R) are in line this line repre-\\nsents the direction which the eye would take normally.\\nThe observer, taking a lighted candle, places it at the fixa-\\ntion point and gradually moves it outward along the inner\\nsurface of the arc until his own eye, directly back of the\\nflame, sees an image of the flame at the center of the pupil\\nof the squinting eye. The degree mark on the arc from\\nwhich the flame was pictured represents the amount of the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0202.jp2"}, "203": {"fulltext": "MUSCLES. 195\\ndeviation or angle of the strabismus this angle being\\nformed by the visual axis with the direction of the normal\\nvisual line. The degree mark on the arc is in front of the\\nFig. 159.\\noptic axis and not the visual axis, but for purposes of\\napproximation they are considered as the same.\\nTreatment of Strabismus. As ametropia is the chief\\nfactor in the cause of squint, this cause must be promptly", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0203.jp2"}, "204": {"fulltext": "I96 REFRACTION AND HOW TO REFRACT.\\nremoved by the use of correcting glasses. The correction\\nof the ametropia means four essentials\\n1. In young subjects the eyes must be put at rest, and\\nkept at rest for two, three, or four weeks, with a reliable\\ncycloplegic and dark glasses. Preference is given to\\natropin in each instance, the writer considering it folly to\\nuse homatropin in such cases.\\n2. During the use of the cycloplegic, the lenses which\\ncorrect the ametropia are selected with care and the greatest\\nprecision, by every known means to this end and just\\nhere is the place of all places to use the retinoscope, as\\nmost cases of strabismus appear in children, and, too, the\\nsquinting eye often being amblyopic, can not assist in the\\nselection of the glass.\\n3. The correcting glasses are ordered in the form of\\nspectacles, and are to be worn from the time of rising until\\ngoing to bed. The strength of the glasses should be as\\nnear the full correction as it is possible to give.\\n4. The drops are continued for a day or two after\\nthe glasses have been obtained, and in this way, while the\\ndrops are still in the eyes, and as their effect slowly wears\\naway, the eyes gradually become accustomed to the new or\\nnatural order of accommodation and convergence. After\\nthe cycloplegic has entirely disappeared, the patient should\\nbe carefully restricted in the use of the eyes for near-work\\nfor several days or weeks.\\nAs hyperopia and astigmatism in combination are gener-\\nally congenital conditions, it therefore follows that conver-\\ngent squint appears quite early in life, as soon as the child\\nbegins to concentrate its vision on near objects. The\\nsquint, at first periodic or intermittent, finally becomes con-\\nstant. Such eyes should be refracted at once, and before\\namblyopia exanopsia can be established. It is interesting", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0204.jp2"}, "205": {"fulltext": "MUSCLES. 197\\nto note that the eyes in many young children begin to fix\\nor lose their squint as soon as cycloplegia is established.\\nThe prognosis is favorable for good vision with glasses\\nwhen this occurs. It will also be observed in other sub-\\njects that while the drops are in the eyes and glasses\\nworn constantly, the squint disappears entirely but as soon\\nas the cycloplegia passes away and near vision is attempted,\\nthe squint returns, and vision falls back in the squinting\\neye to almost the same point that it had before the cyclo-\\nplegia. This occurs in cases where the amblyopia is becom-\\ning established, or where there is a strong muscle devi-\\nating the eye. If the squint is due to amblyopia exanopsia,\\nthen the vision may be improved in one of two ways, as\\nFig. 160.\\nsuggested by Dr. G. M. Gould, Amblyopiatrics, Med.\\nNews, Dec. 31, 1892. One is to use drops in the fixing\\neye, and thus compel the squinting eye to do the seeing\\nor to cover the fixing eye with a blank over the glass (see\\nFig. 160), and have the patient practise in this way for one\\nor two hours each day, using the squinting eye alone.\\nCases that are cured by correcting the ametropia must\\nwear their glasses constantly. Glasses in such cases can\\nseldom be abandoned. In young children the squint re-\\nturns almost at the instant the glasses are removed. The\\nearliest age at which glasses can be prescribed is three years\\nor thereabouts, as it would be unreasonable in most cases\\nto expect a child to appreciate the glasses as anything but a\\ntoy before this age.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0205.jp2"}, "206": {"fulltext": "I98 REFRACTION AND HOW TO REFRACT.\\nThe younger the patient when glasses are prescribed, the\\nmore favorable the prognosis and less likelihood of a ten-\\notomy. The older the patient when glasses are ordered,\\nthe less the likelihood that glasses will cure the squint and\\nthe greater probability of a tenotomy being necessary.\\nThis is explained from the fact that the squint having per-\\nsisted for a long time, the muscle which held the eye in the\\ndeviated position has grown strong and the opposing mus-\\ncle weak.\\nThe correction of squint by glasses applies particularly\\nto cases of the concomitant (convergent or divergent) form.\\nVertical squint is seldom cured by correcting glasses alone.\\nPrisms will occasionally substitute for an operation.\\nMonocular and alternating squint are greatly relieved\\nby the correction of the ametropia, and may or may not\\nbe cured with glasses alone.\\nPeriodic or intermittent squint, if due to permanent opaci-\\nties in the media, can not, as a rule, be cured by any form\\nof treatment.\\nParalytic squint is not a part of the subject-matter of this\\nwork. Cases of concomitant squint are generally amenable\\nto operative treatment, whereas cases of paralytic squint are\\nnot.\\nIt may be stated as a good rule to follow that no case\\nshould ever be operated upon until the glasses which cor-\\nrect the ametropia have been worn constantly for several\\nweeks after all apparent improvement has ceased. If cases\\nfor operation can be selected, the best age is about puberty,\\nwhen the muscles have reached a fair state of development.\\nIf the squint is due to an anatomically short muscle, then\\nthere need not be any great delay in operating after glasses\\nhave been ordered.\\nWhenever a tenotomy has been performed, the eyes", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0206.jp2"}, "207": {"fulltext": "MUSCLES. 199\\nshould again be carefully refracted, as it is a well-estab-\\nlished fact that tenotomy often relieves a tension that will\\nmaterially change the radius of corneal curvature and\\nhence the amount of the astigmatism and the cylinder axis\\nwill be altered.\\nTenotomy. For convergent squint, if of moderate\\ndegree, division of the tendon of the internus of the con-\\nverging eye may be sufficient but if the squint is consider-\\nable, the tendons of both interni may have to be divided.\\nOccasionally, it is necessary to divide the internus and\\nadvance the externus.\\nFor divergent squint, if of moderate degree, division of\\nthe tendon of the externus of the diverging eye may be\\nsufficient but if the squint is considerable, the tendons of\\nboth externi may have to be divided. Occasionally, it is\\nnecessary to divide the externus and advance the internus.\\nFor vertical squint, tenotomy of the stronger superior or\\nstronger inferior rectus, or both, may be necessary.\\nIt is good practice in every instance, before rushing\\ninto an operation for squint, to take the field of vision and\\nsearch carefully for a central scotoma, which, if present,\\nshould put the surgeon on his guard against operative\\ninterference with the hope of obtaining any result other\\nthan cosmetic and even then there is grave danger that the\\ncase will soon lapse into the former state of deviation, or\\npossibly deviate in the opposite direction.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0207.jp2"}, "208": {"fulltext": "CHAPTER VIII.\\nCYCLOPLEGICS.\u00e2\u0080\u0094 CYCLOPLEGIA.\u00e2\u0080\u0094 ASTHEN-\\nOPIA.\u00e2\u0080\u0094 EXAMINATION OF THE EYES.\\nA cycloplegic (from the Greek, xuxXoq, a circle, i. e.,\\nthe ciliary ring, and -Xyytj, a stroke is a drug which\\nwill temporarily paralyze the action of the ciliary muscle.\\nA mydriatic (from the Greek, i\u00c2\u00b1u8piaffi enlargement\\nof the pupil is a drug which will temporarily dilate the\\npupil.\\nAtropin will dilate the pupil and also cause a paralysis\\nof the ciliary muscle. Cocain will cause a dilatation of the\\npupil, but will not paralyze the action of the ciliary muscle.\\nA cycloplegic is also a mydriatic, but a mydriatic is not\\nnecessarily a cycloplegic.\\nThe Uses of a Cycloplegic. (i) To temporarily sus-\\npend the action of the ciliary muscle, or to put the eye in\\nsuch a state of rest that all accommodative effort is for a\\ntime suspended while the static refraction is being estimated.\\n(2) The retina and choroid are given an opportunity to\\nrecover from irritation and congestion incident to eye -strain\\neye-stretching There are many different cycloplegics\\nemployed for estimating the static refraction, and each has\\nparticular qualifications for individual cases. Cycloplegics\\nmay be classed as of three kinds (1) those the effect of\\nwhich passes away slowly (2) those the effect of which\\npasses away moderately fast; and (3) those the effect of\\nwhich is very brief.\\nThe first effect of a cycloplegic is its mydriatic quality,\\n200", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0208.jp2"}, "209": {"fulltext": "very,\\n1 5 days\\nIO\\na\\n8\\n8\\n6\\n2\\nCYCLOPLEGICS. 201\\nafter which the accommodative effort is suspended. The\\nparalysis is not permanent. The following table, from Jack-\\nson, shows the length of time paralysis persists and the\\ntime it takes for the ciliary muscle to fully recover\\nAtropin, effect begins to diminish in 4 days complete reco\\nDaturin, 3\\nHyoscyamin, 3\\nDuboisin, 2\\nScopolamin, 12 hours.\\nHomatropin, 12\\nIf a solution of one of the above-mentioned cycloplegics be\\ninstilled into the conjunctival sac of a healthy eye, it will be\\ncarried by the blood- and lymph-vessels at the sclerocorneal\\njunction into the ciliary muscle and iris, where it acts\\ndirectly upon the nerves and ganglia of these structures,\\nand the aqueous humor also receives some portion of the\\ndrug. If cautiously used, the action will be limited to one\\neye, showing that the drug does not pass through the car-\\ndiac- circulation otherwise, the pupil and ciliary muscle of\\nthe fellow-eye would be similarly affected.\\nSome conjunctivas are very sensitive to any of these\\ndrugs, and develop an inflammation so severe in individual\\ninstances as to resemble ivy poisoning of the lids. Duboisin\\nespecially, and hyoscyamin, by absorption, may develop\\nhallucinations and even a loss of coordination.\\nAny cycloplegic, in fact, when carelessly used, may pro-\\nduce very unpleasant symptoms, such as dizziness, dry\\nthroat, flushed face and body (mistaken for scarlatina), rapid\\npulse, a slight rise of temperature, and delirium. To avoid\\nsuch an annoyance, which is apt to reflect discredit upon\\nthe physician and upon the profession in general, the patient\\nshould always be given definite instructions how to use the\\ndrug in each instance. Stopping the use of the drug and", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0209.jp2"}, "210": {"fulltext": "202 REFRACTION AND HOW TO REFRACT.\\napplying cold compresses will relieve the conjunctivitis, and\\nif constitutional symptoms manifest themselves, a dose of\\nparegoric, cooling drinks, a darkened room, and stopping\\nthe use of the drug will soon restore the patient.\\nForm of Prescription.\\nName, Mr. Brown.\\nU Atropin. sulphatis, gr. j\\nAquse dest., f^U-\\nM. Ft. sol. Label, poison drops\\nSiG. One drop in each eye three times a day, as directed.\\nrjt Dropper. Dr.\\nDate, Tuesday, March 14, 1899.\\nThe reason for labeling this prescription poison drops\\nis not to frighten the patient, but to caution him against\\nleaving the medicine around where children may get hold\\nof it, and at the same time to let him understand that it is\\nto be used and handled with care.\\nMr. Brown is told to have one drop put in each eye\\nthree times a day, after meals, and to report at the office on\\nThursday (the prescription is given on Tuesday in this case).\\nThe reason for using the drug for this length of time is to\\ninsure complete paralysis, and also to give the eyes a physi-\\nologic rest. In having these drops put in the eyes, the\\npatient should tip his head backward and turn his eyes down-\\nward, and as the upper lid is drawn up, one drop (from the\\ndropper) \\\\s placed (not dropped) on the sclera at the upper and\\nouter part. After the drops are placed in the eyes, as far away\\nfrom the puncta lachrymalia as possible, the patient holds\\nthe canaliculi closed by gently pressing with the ends of the\\nindex fingers on the sides of the nose at the inner canthi\\nfor a minute or two. If more than one drop enters the eye,\\nit will run over on to the cheek, and should be wiped off.\\nWith children, these instructions are not so easy of exe-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0210.jp2"}, "211": {"fulltext": "CYCLOPLEGICS. 2C 3\\ncution, and the writer has seen a few such clinical subjects\\nflushed and delirious from gross carelessness on the part of\\nparents in dropping the medicine into the inner canthi,\\nwhere it soon passed into the nose, or else the drug is\\nallowed to flow over the cheek and into the child s open\\nmouth. Ordinarily, there need never be any discomfort\\nfrom the use of these drugs beyond a slight dryness of the\\nfauces.\\nCaution. Cycloplegics should never be used when\\nthere is the least suspicion of glaucoma in one or both\\neyes. Cycloplegics should not be used in the eyes\\nof nursing women such patients are peculiarly suscep-\\ntible to the action of these drugs, and the mammary\\nsecretion may thereby be diminished in amount. After the\\nage of forty-five or fifty years, or in the condition known\\nas presbyopia, it is seldom necessary to use a cycloplegic.\\nIf a cycloplegic is necessary in presbyopia, one of the\\nweaker drugs is generally employed.\\nIn the selection of a cycloplegic the surgeon must be\\nguided by the patient s occupation, age, the character of\\nthe eyes, and the refraction. From the foregoing table it\\nwill be seen that atropin and daturin are slow in passing\\nfrom the eye, making their employment on this account\\nvery objectionable in many instances. The accommodation\\nreturns sooner after the use of hyoscyamin and duboisin\\nthan from atropin, but not so promptly as from scopolamin\\nand homatropin. The effect of the latter is very brief. A\\npatient who might lose his business position if he remained\\naway from work for more than a week could not afford to\\nhave atropin or daturin used in his eyes, whereas a school\\nchild might accept atropin as a luxury. The man of busi-\\nness, the cashier in a bank, the storekeeper, and others\\nmust, in many instances, have their eyes refracted in at", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0211.jp2"}, "212": {"fulltext": "204 REFRACTION AND HOW TO REFRACT.\\nleast two days and this latter time means, of course, the\\nuse of homatropin. The nearer the age to forty years, the\\nless need for one of the stronger cycloplegics, as the power\\nof accommodation has markedly diminished at this period\\nof life, so that hyoscyamin or scopolamin will answer every\\npurpose. After thirty-five years homatropin can, as a rule,\\nbe relied upon as a cycloplegic.\\nIn hyperopic eyes of young subjects it is useless to em-\\nploy homatropin, as the active ciliary muscle requires a\\nstrongly acting cycloplegic to stay the accommodative\\npower. In myopic eyes one of the stronger cycloplegics\\nmay be used to advantage, for the following reasons\\nMyopic eyes have large pupils, as a rule, and do not mind\\nthe mydriasis myopic eyes are often in a state of irritation,\\nand the drug gives them a much-needed rest the myope s\\ndistant vision is not disturbed by the cycloplegic, as in the\\ncase of the hyperope.\\nWhenever a cycloplegic is prescribed, the patient should\\nbe ordered a pair of smoked-glass spectacles to wear dur-\\ning the mydriasis. Of the two forms of smoked glasses,\\ncoquilles and plane, the latter should always be preferred,\\nas they are without any refractive quality, whereas coquilles\\nhave some form of refraction that may act very injuriously.\\nAnother reason for ordering the plane glass is that the\\npatient will often wish to wear them with his prescription\\nglasses, which he could not do so well if they were coquilles.\\nDark glasses are of four shades of London smoked A\\nB, C, and D, A being the lightest shade and D the darkest.\\nThe prescription would be\\nFor Mr. Brown\\nR One pair plane London smoked D.\\nSlG. For temporary use. Dr.\\nMarch 14, 1899.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0212.jp2"}, "213": {"fulltext": "CYCLOPLEGICS.\\n205\\nThe cycloplegics above mentioned for purposes of re-\\nfraction are ordered in the following strengths\\nAtropin. sulphatis,\\nDuboisin. sulphatis,\\nHyoscyamin. sulphatis,\\nDaturin. sulphatis,\\nScopolamin. hydrochlor.\\ngr. j to aq. dest.\\ngr. ss\\ngr. ss\\ngr. ss\\ngr. j\\nf 3 iss.\\nAll these, except scopolamin, are ordered to be used\\nthree times a day, preferably after meals but scopolamin\\nbeing a very powerful drug, the surgeon should place it in\\nthe patient s eyes himself in the office, and not give a pre-\\nscription for it. Only two drops are necessary, and are\\ninstilled a half-hour apart, the static refraction being esti-\\nmated one hour after using the second drop.\\nHow to Use Homatropin. This drug is expensive, and\\nit is never necessary to prescribe more than one grain for\\nany one patient. Personally, the writer has found the fol-\\nlowing most satisfactory, though the strength of the homa-\\ntropin may be increased if desired\\nFor Miss Robinson\\nR Homatropin hydrobromate,\\nAq. dest.\\nM. Ft. sol. Label, poison drops\\nSiG. One drop in each eye, as directed.\\nR Dropper.\\nMarch 14, 1899.\\ngr-J\\nnt xl.\\nDr.\\nOne drop of this solution instilled into a healthy eye will\\nproduce mydriasis in a few minutes, but its action on the\\nciliary muscle is so trifling that the near point will be but\\nslightly changed. It is thus shown that this drug is a\\ndecided mydriatic, and only becomes a cycloplegic under\\ndefinite usage.\\nTo produce cycloplegia with homatropin, the patient is", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0213.jp2"}, "214": {"fulltext": "206 REFRACTION AND HOW TO REFRACT.\\ngiven the above prescription and told to use it as fol-\\nlows\\nTo place one drop in each eye at bedtime the first night.\\nThis one drop dilates the pupil and establishes a change in\\nthe circulation of the blood-supply to the iris and ciliary\\nbody a very important matter for the patient s comfort, and\\nat the same time preventing a tendency to spasm of the\\nciliary muscle. The next morning one drop is to be placed\\nin the eye every hour, from the time of rising until leaving\\nhome to go to the surgeon s office. At the office one drop\\nis placed in each eye about every five minutes, until six\\ndrops have been used then, after waiting half an hour\\n(for the cycloplegic effect, which will last for one hour), the\\nrefraction is carefully estimated. After a short interval the\\ncycloplegic effect will begin to rapidly disappear, so that the\\npatient will be able to read within forty-eight hours time\\nwith his correcting glasses.\\nOccasionally, a busy patient will insist upon having his\\neyes refracted during his first visit, and can not take time\\nto use the drops in the manner above suggested. The\\nsurgeon must, therefore, start and use the drops in his\\noffice. This is forcing the ciliary muscle into a state of\\nparalysis that does not always give ultimately satisfactory\\nresults. Forcing homatropin into an eye in this way\\nwill always produce a bloot-shot eye (hyperemia of the\\nconjunctiva, etc.) that does not improve a patient s appear-\\nance and it often produces severe neuralgic headache that\\nmay result in nausea or vomiting in occasional instances.\\nFurthermore, it is possible, with a drug like homatropin, if\\nnot properly used, to have some of the sphincter-fibers\\nbecome paralyzed while others may rerrfain free to act. In\\nthis way a spasm of the ciliary muscle may be produced\\nthat will give a false astigmatism. Personally, the writer", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0214.jp2"}, "215": {"fulltext": "CYCLOPLEGICS. 20J\\nis not partial to this method of forcing the ciliary muscle\\ninto repose.\\nTo somewhat obviate the blood-shot condition of the\\neye, and also to assist the action of the forcing process,\\none drop of a two or four per cent, solution of cocain\\nmay be instilled while the homatropin is being used. This\\nalso diminishes the danger of spasm. But cocain is objec-\\ntionable in that it will, in some cases, haze the cornea.\\nThe retinoscope will show this, and the patient will state\\nthat, while he can see the letters on the test-card, yet they\\nhave a mist over them. Instead of using the hom-\\natropin alone, a small amount of cocain may be added to the\\nsolution for the purpose mentioned. Or, homatropin may\\nbe combined with cocain and chlorid of sodium in the form\\nof a disc, and one of these, placed in the conjunctival sac, is\\nallowed to dissolve, and in this way paralyze the accommo-\\ndation. Or, homatropin may be used in a solution of dis-\\ntilled castor oil. It is claimed that when the drug is used\\nin this form, it remains in contact with the tissues and acts\\nmore energetically.\\nHomatropin as a cycloplegic should be held in reserve\\nfor individual cases, and not used as a routine practice. It\\nis a good, reliable paralyzer of the accommodation in many\\neyes at \u00c2\u00a3he age of thirty-five, or thereabouts but in a young\\nhyperopic eye it is a waste of time to attempt successful\\nparalysis with it, and the danger of producing a false astig-\\nmatism should certainly deprecate its use in these cases.\\nAnother very serious objection to its use is that before the\\neyes can become accustomed to the prescription glasses,\\nthe ciliary muscle recovers and begins to accommodate,\\nwith the result that the patient says he can see better at a\\ndistance without his glasses than he can with them, and\\nhas no small amount of mistrust of the surgeon s ability,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0215.jp2"}, "216": {"fulltext": "208 REFRACTION AND HOW TO REFRACT.\\nas he will have to wear his glasses a long time before his\\nciliary muscle will relax its accustomed accommodative\\nefforts. This is not nearly so likely to occur if one of the\\nslowly acting cycloplegics is used.\\nThe method of refracting with one of the slowly acting\\ncycloplegics, and then endeavoring to counteract the effect\\nwith a solution of eserin, is not recommended. Temporarily,\\neserin may overcome the cycloplegic but as its action is\\nonly transitory, the paralysis reasserts itself and will not\\ndisappear until the specified time.\\nRefracting one eye at a time with a cycloplegic while the\\npatient pursues his occupation with the other eye is not a\\nmethod to be considered. This means a great amount\\nof discomfort, headaches, eye-strain, and even diplopia at\\ntimes, during so prolonged a treatment.\\nIf a hyperopic patient must occasionally use his eyes for\\nnear work while he has drops in them, a pair of +3 or\\n-f 4 spheres may be given for temporary use.\\nCycloplegia.\\nCycloplegia is a paralysis or paresis of the ciliary muscle.\\nThis condition may be monocular or binocular it may be\\npartial or complete. Mydriasis may or may not accompany\\nthe cycloplegia, though the two conditions usually occur\\ntogether and when they both exist, the paresis is spoken\\nof as ophthalmoplegia interna. The ciliary muscle and\\nsphincter of the iris are controlled by branches from the\\nthird nerve but these branches are from independent cen-\\nters the fibers going to the ciliary muscle arise beneath the\\nfloor of the third ventricle, in front of the fibers which go to\\ncontrol the sphincter of the iris.\\nCauses. Temporary paralysis of the ciliary muscle and\\niris, as already stated, will result from the external or internal", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0216.jp2"}, "217": {"fulltext": "CYCLOPLEGIA. 209\\nadministration of a cycloplegic. It is interesting, in many\\ncases, to find the cause and relieve the patient s anxiety\\nwhen the paresis is due to one of the cycloplegics. Aside\\nfrom the use of eye-drops, the question of external\\nmedication (liniments, ointments, and plasters) should be\\ninquired into, as also whether rectal or vaginal supposi-\\ntories containing a cycloplegic have been used.\\nOther causes of this form of paralysis are tonsillitis, quinsy,\\ndiphtheria, Bright s disease, rheumatism, gout, exhausting\\ndiseases, blows upon the eye, etc. Other and more serious\\ncauses, as controlling a guarded prognosis, are intracranial\\nhemorrhage, meningitis, syphilis, brain tumor, etc. In\\nsome instances the cause can not be definitely ascertained.\\nSymptoms and Diagnosis. Photophobia, dilatation of\\nthe pupil, and loss of accommodative power consistent with\\nthe optic condition of the eye.\\nA myopic eye retains its vision at the far point only an\\nemmetropic eye or a hyperopic eye wearing correcting\\nglasses has good distant vision and absence of a near\\npoint an uncorrected hyperopic eye has poor distant and\\nnear vision.\\nPrognosis. This depends upon the cause.\\nTreatment. This must be symptomatic and expectant,\\nwith a removal of the exciting cause, if possible. As many\\ncases of cycloplegia are the result of, or follow, an attack of\\ndiphtheria, or a disease which has reduced the system below\\npar, tonics, fresh air, etc., must be ordered. When brought\\non by syphilis, mercury and iodid of potash must be\\nprescribed. Dark glasses for the photophobia should\\nalways be ordered, and lenses for near-work may be worn\\nas a temporary expedient. The use of eserin locally will\\noccasionally do good work, but is not advised for constant\\nuse or for every case. Faradism may be used if the cyclo-\\n18", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0217.jp2"}, "218": {"fulltext": "210 REFRACTION AND HOW TO REFRACT.\\nplegia is very persistent, but the best results may be ex-\\npected from systemic treatment. The use of strychnin or\\nnux vomica are recommended in certain instances.\\nCramp of the Ciliary Muscle.\\nCramp of the ciliary muscle is the opposite condition to\\nthat of cycloplegia, just described. Ciliary cramp may\\noccur in one or both eyes, usually in both it may occur\\nin any form of ametropia or in emmetropia. Ciliary\\ncramp is of two kinds clonic and tonic.\\nClonic cramp is an occasional and temporary condition\\nwhich comes on while the eyes are in use, and passes away\\nsoon after the eyes have had an opportunity to rest, and\\nmay not occur again for several days.\\nTonic cramp, also called spasm of the accommodation,\\nis a permanent condition as compared with the clonic form,\\nand occurs whenever the eyes are used for distant or near\\nvision. The patient can not use his eyes for any length of\\ntime, or with any considerable concentration, without suffer-\\ning as a consequence.\\nCauses. Clonic cramp may occur as one of the early\\nsymptoms of presbyopia. Ametropia is a very common\\ncause, and especially in cases of low amounts of hyperopia\\nor myopia. Emmetropia, or eyes made emmetropic with\\nglasses, may develop clonic or even tonic cramp if the eyes\\nare used to excess or in a bad light. Such cases have been\\ncalled hyperesthesia of the retina. Tonic cramp may\\ndevelop from the same causes which bring on the clonic\\nform, and is usually seen among young hyperopic children,\\nor the pseudo-myope already described. It also occurs\\noccasionally in hysteric patients or those recovering from\\nsome severe or long illness. The writer has seen this form", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0218.jp2"}, "219": {"fulltext": "CRAMP OF THE CILIARY MUSCLE. 211\\nof cramp precede or antedate by several weeks a collapse\\nof the nervous system i. c, nervous prostration.\\nSymptoms. Naturally, ciliary cramp means ocular\\npains and headaches. Opera headache, train headache,\\nshopper s headache, bargain-counter headache, etc.,\\nare some of the many names given to cramp of the ciliary\\nmuscle, and are, no doubt, the result of accommodative effort\\nin a bright light or watching moving objects, these symp-\\ntoms being a part of the history of accommodative astheno-\\npia (already described) and accompanying insufficiency of the\\nmuscles. Symptoms of myopia are very evident during the\\ncramp. In the tonic cramp the ocular pains and headache\\nmay be so excruciating in individual cases as to make the\\nfamily physician and patient dread cerebral disease until the\\nimmediate cause is found out.\\nTreatment. As the cause is usually one of ametropia,\\nthis must be corrected by the careful selection of glasses\\nwhile the eyes are undergoing a prolonged rest with a\\ncycloplegic and dark glasses. Later on the patient must be\\ncautioned against any overuse of the eyes. The general\\nhealth should have any necessary attention. Sedatives,\\nalteratives, and tonics have their place in individual cases.\\nReflex causes must be looked for and, as far as possible, re-\\nmoved. Insufficiencies should always be carefully searched\\nfor, and frequently prism exercises to develop the strength\\nof the weak muscles may give marvelous results. Un-\\nfortunately, there are occasional instances of tonic cramp\\nthat persist in spite of any treatment, and such cases obtain\\nrelief only when presbyopia definitely asserts itself.\\nAsthenopia (from the Greek, d, priv. rOho^, strength\\nwv eye means a weakness or fatigue of the eye, applying\\nespecially to the retina, the ciliary muscle, the extra-ocular\\nmuscles, or a general weakness of any one or two or all", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0219.jp2"}, "220": {"fulltext": "212 REFRACTION AND HOW TO REFRACT.\\nof these structures in one and the same eye. Asthenopia\\nis a disease, and is often spoken of as weak sight, eye-\\nstrain, or eye-stretching.\\nVarieties. For purposes of study, differential diagnosis,\\nand treatment, asthenopia, or eye-strain, has been divided\\ninto the following varieties Retinal, muscular, accommo-\\ndative, and asthenopia due to a combination of any two or\\nall three varieties.\\nRetinal Asthenopia. This is the rarest form of asthen-\\nopia, and usually occurs in females. It is brought about\\nby overuse of the eyes in too dim or too bright a light,\\nand may result from a too prolonged use of the eyes at any\\nkind of work or in any kind of light. It may result from\\nexposure to the sun s rays, to electric lights, or to light-\\nning, or by reflection from bright objects, such as snow,\\netc. Retinal asthenopia may occur as a symptom of hys-\\nteria, or in a patient whose nervous system is peculiarly\\nsusceptible to vibrations, sounds, and lights in a patient\\nwhose nervous system is an uncertain quantity. Such pa-\\ntients are very unsatisfactory to treat or even to examine\\nthey often imagine that the reflected light from the ophthal-\\nmoscope or retinoscope is very hot, etc.\\nSymptoms. The chief symptom is a dread of light\\n(photophobia), or photophobia and lacrimation together.\\nTreatment. The first thing to do is to remove the\\ncause, if this can be found otherwise the treatment should\\nbe very conservative. Ametropia must be corrected and\\nthe eyes be given some regular work in other words, it is\\nnot good practice to restrict all use of the eyes. The treat-\\nment with tinted glasses, made so much of by the char-\\nlatan to gull the innocent public, should not be ordered,\\nas the patient grows accustomed to them and they event-\\nually become an absolute necessity on all occasions. Care-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0220.jp2"}, "221": {"fulltext": "CRAMP OF THE CILIARY MUSCLE. 2 13\\nful attention to the general health is certainly indicated\\ntonics, out-door sports, etc., should be prescribed in\\nindividual cases. The shade of the trees is to be recom-\\nmended in preference to the seashore and bright reflection\\nfrom the sand and water.\\nMuscular Asthenopia. This is due to weakness or\\nfatigue of one or more of the extra-ocular muscles, most\\nfrequently the interni (exophoria). Muscular asthenopia\\nof the exophoric kind is the result, as a rule, of a want of\\npower to maintain convergence. The symptoms are in\\nkeeping with a cramp followed by a relaxation of converg-\\ning power. Ocular pains, eyeballs tender to the touch (per-\\nchance the internal recti themselves become sore to the\\ntouch or feel sore on movement of the eyes), and in some\\ncases the conjunctiva and subconjunctival tissues overly-\\ning the muscles become hyperemic during or after the use\\nof the eyes, simulating rheumatism of these structures. In\\nother cases dim vision and diplopia will be occasional mani-\\nfestations. Patients with muscular asthenopia occasionally\\nfind that they can continue at near work by using one eye,\\nbut this does not occur very often.\\nTreatment. This resolves itself into the correction of\\nthe ametropia, exercise of the weak muscles, etc. (See\\nchapter on Muscles.)\\nAccommodative Asthenopia. This is by far the most\\ncommon form of asthenopia, and is due to fatigue of the\\nciliary muscle it is, therefore, to be expected in hyperopic\\neyes. It is caused in various ways from overuse of the\\neyes in too bright or too dim a light, or from using the eyes\\nfor too long a time in any kind of a light. The best pair\\nof eyes, if overtaxed, may suffer from accommodative\\nasthenopia, even when wearing the ametropic correction.\\nOr accommodative asthenopia may result from a weakness", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0221.jp2"}, "222": {"fulltext": "214 REFRACTION AND HOW TO REFRACT.\\nof the ciliary muscle as a part of the general condition of the\\nwhole body, and this may come on after or during some long\\nillness, such as typhoid fever. Accommodative asthenopia\\nis often present in the early months of presbyopia.\\nSymptoms. The principal symptom is headache fron-\\ntal, frontotemporal, or fronto-occipital or this pain or dis-\\ncomfort may extend into the neck or between the shoulders.\\nThe headache develops during the use of the eyes, and\\ngrows worse if the effort is prolonged, and usually ceases\\nafter the eyes are rested. See chapter on Hyperopia and\\nMyopia.\\nTreatment. When glasses are necessary, they should\\nbe ordered by the static refraction. The general health of\\nthe patient should receive careful attention. An out-of-\\ndoor life will often be necessary, and in certain cases the\\ntime for using the eyes at any near-work will have to be\\nvery much restricted.\\nAccommodative with Muscular Asthenopia. This\\nvariety of asthenopia embraces the two forms just men-\\ntioned, and its description and treatment are included in both.\\nReflexes Due to Eye-strain. Among the symptoms\\nof the various forms of asthenopia described on the previous\\npages, the writer has avoided any decided reference to reflex\\nsymptoms, preferring to speak of these reflexes in a general\\nway under one heading. Many patients who suffer from\\nheadaches, ocular pains, etc., during the use of their eyes,\\nalso very frequently suffer from constipation, indigestion,\\nheartburn, nausea, or even vomiting. Other patients\\nmay have nervous attacks, a fear of some impending\\ncalamity, or they are irritable or despondent they may\\nsuffer from insomnia, or, if they sleep, it is not a restful\\nsleep. Others may have epileptic attacks, nervous twitch-\\nings, etc. To just what extern eye-strain is responsible for", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0222.jp2"}, "223": {"fulltext": "EXAMINATION OF THE EYES. 21 5\\nthese and many other reflexes the writer is not prepared\\nto say, though every ophthalmologist has certainly seen\\nsome cases of accommodative and muscular asthenopia with\\ngastric symptoms, or nervous symptoms, or epileptic\\nattacks, or irritable tempers, or insomnia, or enuresis, etc.,\\nin which these reflex symptoms entirely disappeared after\\nthe eye -strain was properly treated.\\nExamination of the Eyes.\\nA systematic method should be pursued in the examina-\\ntion of the eyes, and the results recorded in a book or on\\na card prepared for that purpose. The student should be\\na careful observer, and also be able to question the patient\\nintelligently for short and definite answers. The following\\nis an excellent method of making records, but there is no\\narbitrary rule, and in this respect each surgeon may follow\\nhis own desires\\nDate,\\nName,\\nResidence,\\nOcaipation,\\nAge, Sex, Diagnosis,\\nAccommodation. Astigmatism. Muscles.\\nO. D. V., p. p.\\nO. S. V., p. p.\\nHistory,\\nS. P. {status prcesens, present condition Inspection,\\nOphthalmometer, O. D O. S\\nOphthalmoscopic examination, O. D. O. S\\nManifest refraction. Fields. Color sense. R", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0223.jp2"}, "224": {"fulltext": "2l6 REFRACTION AND HOW TO REFRACT.\\nThe above record is filled out as the examination pro-\\nceeds, but it is not always advisable to follow the exami-\\nnation in the order given on the contrary, it is better, after\\ngetting the patient s name and address, to ask certain other\\nquestions which may appear in keeping with an individual\\ncase.\\n1. Occupation. This is a very important question, as\\nbearing directly upon the amount and character of work\\ndone by the eyes for example, writing, reading, sewing,\\nmusic, engraving, weaving, drafting, surveying, painting,\\ntypewriting, typesetting, sorting colors, etc.\\n2. Age. This is of the utmost importance in comparing\\nthe range of accommodation (near point) with the emme-\\ntropic condition. Knowing the patient s age and near point\\nwill often give a diagnosis of the character of the refraction.\\n3. The name tells the sex, but the question really is\\nwhether the patient is married, single, widow, or widower.\\nIf a young married woman, whether she is nursing a young\\nchild.\\n4. History. Under this heading the questions should\\nbear directly upon the eyes. In what way do the eyes\\ncause trouble? The usual answer to this question is\\nlicadaclie. To get a complete history of the headache,\\nand be able to differentiate it from headache due to other\\ncauses, the succeeding questions seem appropriate\\nWhat part of the head aches Is it frontal, occipital,\\ntemporal, interocular, vertex, or all over the head\\nWhen does the headache come on during or after\\nthe use of the eyes Does it cease after resting the eyes\\nIs the headache worse when using the eyes by artificial\\nlight Is the headache constant Is it periodic Is it\\nworse at a certain hour of the day Is the headache pres-\\nent when first waking in the morning Does the head ache", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0224.jp2"}, "225": {"fulltext": "EXAMINATION OF THE EYES. 217\\nduring or after attending a place of public amusement or\\nwhen shopping If a female, is the headache only monthly\\nThe ophthalmologist must not think because a patient has\\na headache that it is surely and always due to the eyes, and\\nthat glasses are going to cure it. It is for the ophthalmolo-\\ngist to find out just what part the eyes take in causing the\\npatient s discomfort, and not always expect to cure with\\nglasses headaches that have no direct relation to the eyes.\\nOne of the most common causes of headache which\\nmay be mistaken for ocular headache is the brow ache\\ndue to malaria, but a history of previous malarial attacks,\\nchills and fever, a residence in a malarious district, and the\\nfact that it is periodic in character, should certainly give a\\nclear differential diagnosis.\\nOther patients may not consult the ophthalmologist on\\naccount of headache, but for a pain in or back of the eyes,\\nor back part of the head, or between the shoulders, which\\ncomes on after any effort of vision. Others may complain\\nof a feeling of sand in the eyes, or a burning in the lids, or\\na smarting or itching in the lid margins, or excessive lacri-\\nmation, or a feeling of drowsiness as soon as the eyes are\\nused for any length of time, or a feeling as if the eyelids\\nwould stick to the eyeballs.\\nThe patient s seeing qualities may develop the history of\\npoor distant vision and good near vision, or vice versa this\\nshould be inquired into very carefully, and it may be well\\nto ask about other members of the family, if they have the\\nsame condition. Or a history of the vision gradually fail-\\ning or of a sudden loss of sight may be obtained, and pres-\\nbyopic symptoms should be referred to, if the patient is\\nover forty years of age.\\nIf the patient wears glasses, it is well to inquire whether\\nthey were ordered by an ophthalmologist or if they are\\n19", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0225.jp2"}, "226": {"fulltext": "2l8 REFRACTION AND HOW TO REFRACT.\\nthe patient s own selection. In the former instance a record\\nshould be made of the character and strength of the lenses,\\nand whether the lenses were ordered with or without\\ndrops in the eyes; and if drops were used, if the\\neffect lasted for two days or longer (slowly or quickly\\nacting cycloplegic). Ask how long the glasses have been\\nworn, and if the same symptoms are present that existed\\nwhen the lenses were previously ordered.\\nHaving made a note of the patient s history, it is next in\\norder to study the present condition {status prcesens)\\n1 Breadth of face, its symmetry or asymmetry inter-\\npupillary distance.\\n2. The eyelids, whether swollen, discolored, or having\\nred margins.\\n3. The eyelashes (cilia), whether regular, irregular, or\\nabsent. If there are chalazia, styes (hordeola), inflammation,\\nmoist or dry secretion at the roots of the cilia (blepharitis).\\n4. Inspect the inner surface of the lids and ocular con-\\njunctiva for inflammation or growths.\\n5. Inspect the lacrimal apparatus in all- its parts.\\n6. Inspect the cornea for its polish, transparency, and\\nregularity.\\n7. Depth of the anterior chamber.\\n8. Iris, its color and mobility.\\n9. Pupil, its size, shape, and position.\\n10. Color of reflex from the pupillary area.\\n1 1 Palpate to measure the intraocular tension.\\n12. Use the cover test at 13 inches for any muscular\\nanomaly.\\nFollowing this record of the history and present condi-\\ntion, the distant vision and near point are taken for each\\neye, one or more tests for astigmatism are made, the mus-\\ncles are tested for distance (six meters), and the ophthal-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0226.jp2"}, "227": {"fulltext": "EXAMINATION OF THE EYES. 2IO,\\nmometric measure of corneal curvature may be recorded.\\nFinally, and most important of all, the ophthalmoscopic\\nexamination is made, and the cornea, aqueous, lens cap-\\nsule, lens, vitreous, nerve (shape, size, color, cupping, and\\nvessels), conus, macular region, etc., and periphery of the\\neye-ground are studied.\\nLastly, fields and color sense, dynamic or manifest re-\\nfraction.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0227.jp2"}, "228": {"fulltext": "CHAPTER IX.\\nHOW TO REFRACT.\\nGeneral Considerations. Before placing lenses in front\\nof an eye, the surgeon should be acquainted with at least\\nfive important facts\\n1. The Patient s Age. This tells at once, from the\\ntable on page 69 (which the surgeon should commit to\\nmemory), what the near point will be if the eyes are emme-\\ntropic or standard.\\n2. The Near Point. This will usually indicate hyper-\\nopia if beyond, and myopia if closer than, the emmetropic\\nnear point for the age.\\n3. The Distant Vision in Each Eye. If very defective,\\nor if less than and near point closer than the age calls\\nfor, myopia is indicated. Good distant vision and near\\npoint removed indicate hyperopia.\\n4. The distant vision, if recorded with question\\nmarks, usually indicates astigmatism.\\n5. The Results of Testing with the Astigmatic\\nChart. Darkest lines from XII to VI, or I to VII, or XI\\nto V, indicate astigmatism (myopic) with the rule or\\ndarkest lines from IX to III, or VIII to II, or X to IV,\\nindicate astigmatism (hyperopic) with the rule.\\nIt is well to remember that about four patients out of\\nfive have hyperopia, or one patient in five has myopia, and\\nthe minus sphere selected almost invariably requires a\\ncylinder in combination. Remember, also, that astigma-\\ntism is usually with the rule and symmetric, and that plus\\n220", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0228.jp2"}, "229": {"fulltext": "HOW TO REFRACT. 221\\ncylinders are generally selected at axis 90 or within 45\\ndegrees either side of 90, and minus cylinders are gen-\\nerally selected at axis 180 or within 45 degrees either side\\nof 180.\\nThe Placing of Trial-lenses. 1. These should always\\nbe placed as close as possible to the eyes without interfer-\\ning with the lashes and to accomplish this, the trial-frame\\nshould be easy of adjustment.\\n2. The center of the trial-lens must be opposite to the\\ncenter of the pupil.\\n3. If the distant vision is very defective,\\nor a strong- lens of 2, 3, or 4 D. will often be re-\\nXL LX u -r\\nquired whereas, if the vision is or a weaker lens\\nwould be called for.\\n4. When a spheric lens placed before an eye improves the\\nvision, it should not be changed for another unless the vision\\nis made better by having its strength increased or dimin-\\nished by placing in front of it another sphere (plus or\\nminus) of less strength. For instance, if a +2 sph. has\\nbeen placed before the eye and the vision is improved from\\n^x~ to vn\u00c2\u00a7s t 1 s 2 s Pk should not be changed until a\\n0.50 or 0.50 sph. has been held in front of it and the\\npatient states whether he can read more with it or less without\\nit. When a vision of is approximated, then its accuracy\\nmust be determined by placing first a -[-0.25 and then a\\n0.25 in front of the correction, so as to learn from the\\npatient which one, if either, of these lenses improves the\\nvision. Or if the correcting lenses selected are weak ones,\\nthen 0.12, plus and minus, may be used in place of the\\n0.25.\\n5. Spheric lenses should always be tried before using\\ncylinders, and the vision brought as low as possible with", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0229.jp2"}, "230": {"fulltext": "222 REFRACTION AND HOW TO REFRACT.\\na sphere before combining a cylinder, and, in fact, after\\nthe vision has been improved as much as possible with\\na sphere, the pointed line-test for astigmatism may be\\nbrought into use, as very often low errors of astigmatism\\nare not recognized until this point in the refraction has\\nbeen reached. Advocates of the ophthalmometer place\\nthe cylinder before the patient s eye and then add the\\nspheric correction. The writer is not partial to this method\\nor way of refracting.\\n6. When a patient miscalls one or more letters in a cer-\\ntain line, the surgeon must not hurry on until these are\\ncorrected by the patient with a suitable glass, and in\\nthis way the refraction is gradually worked out until the\\nvision is brought to the greatest acuity possible. It is\\nnever wise to stop with a vision of as we are often able\\nto get a visual acuity of or occasionally\\n7. Cylinders. When a plus cylinder is employed, it is\\nplaced with its axis at 90, and then slowly revolved (if nec-\\nessary) to an axis where the patient says he can see better.\\nA minus cylinder is placed at axis 1 80, and revolved in the\\nsame manner. The rule (4) for changing spheres also ap-\\nplies to cylinders i. e., to increase or decrease the strength\\nof the cylinder by placing in front of it a plus or minus\\ncylinder of less strength at the same axis.\\n8. Axis of the Cylinder. When a patient is not sure\\nabout an exact axis, though he is sure that the cylinder\\nimproves the vision, then the surgeon may employ a sphere\\nof the strength of the sphere and cylinder combined, and\\nuse a cylinder of the same strength as before, but with\\nopposite sign and at about the opposite axis. For example,\\nwith +2.25 sph. O +0.75 cyl., the patient is not sure if\\nthe vision is best with the axis at 35, 40, or 45, the sur-\\ngeon must then use a +3.00 sph. O 0.75 cyl., when the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0230.jp2"}, "231": {"fulltext": "HOW TO REFRACT. 223\\nexact axis (at right angles) will usually be selected without\\nany hesitancy or doubt.\\n9. Proving the Correction. All tests at the trial-case,\\nwhen a cycloplegic is used, should be confirmed with the\\nretinoscope.\\n10. Crossed Cylinders. This is a trial-lens that has\\none meridian minus and the opposite meridian plus. They\\nare made of any strength, but for general use the 0.25 cyl-\\ninders are employed i. e., 0.25 sph. O +0.50 cyl. The\\npurpose of the crossed cylinders is to increase the refrac-\\ntion in one and diminish it in the opposite meridian. For\\nexample: if +2.00 sph. O+1.00 cyl. axis 90 gives a\\nvision of ^j^, and the crossed cylinder lens is placed in\\nfront of this combination with 0.25 at axis 180, and the\\n-^0.25 at axis 90, and the vision comes down to it\\nshows that the vertical meridian was 0.25 too strong, and\\nthe horizontal 0.25 too weak, and the result would be\\n-f 1.75 sph. O +1.50 cyl. axis 90 degrees. Or, if 3.00\\nsph. has brought the vision to and the crossed cylinder\\nlens is placed before it and rotated to axis 1 5 for the\\nminus cylinder and axis 105 for the plus cylinder, and the\\nvision comes to the result would be 2.75 sph.\\nO 0.50 cyl. axis 15.\\nMethods of Estimating Refraction. To determine\\nthe refraction of an eye it may or may not (as in presby-\\nopia) be necessary to employ a cycloplegic. When the\\nrefraction is estimated without a cycloplegic, it is spoken of\\nas manifest or dynamic (Gr., duva[iiq i power refraction.\\nWhen a cycloplegic is used, the refractive estimate is spoken\\nof as static (Gr. ffrarizoz, from, iqrdvai, to stand at rest In\\none instance the ciliary muscle is permitted to act, and in\\nthe other it is at rest. A third method is to obtain the\\nstatic refraction and then to estimate the strength of the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0231.jp2"}, "232": {"fulltext": "224 REFRACTION AND HOW TO REFRACT.\\nglasses to be prescribed after the effect of the cycloplegic\\nhas passed out of the eyes this is spoken of as post-\\ncycloplegic refraction. Eyes for refraction are divided into\\ntwo general classes, according to the age of the patient. In\\nthose under forty-five years of age a cycloplegic is usually\\nemployed, but after this age a cycloplegic is often dis-\\npensed with. (See Presbyopia.)\\nManifest or Dynamic Refraction. This method is\\noften pursued with the idea or purpose of obtaining some\\napproximation of what the character of the refraction may\\nbe, and never for the purpose of prescribing glasses except\\nin presbyopia, and some few exceptional cases as a tempo-\\nrary expedient. The routine habit of prescribing glasses\\nfrom the manifest refraction without any knowledge of the\\nophthalmoscopic record is not a method that merits the\\nattention of the conscientious physician. Such work is\\nvery unscientific, often leading to gross errors, ultimate\\ndissatisfaction of the patient or injury to the eye.\\nPostcycloplegic Refraction. The ordering of glasses\\nafter the static refraction has been recorded and the effect of\\nthe cycloplegic has left the eyes. For instance While the\\nciliary muscle is paralyzed with atropin the static refraction\\nis found to be +1.50 sph. O 2 -(X) cyl. axis 90 degrees,\\nwhich gives a vision of The atropin is then stopped\\nand the patient told to report in fifteen days, when the ciliary\\nmuscle will have regained its original strength and gone\\nback to its old habit of accommodating for distance. The\\nstatic refraction is placed before the eyes, and the strength of\\nthe sphere is gradually reduced until the vision just equals\\nas it was when the drops were in the eyes. What-\\never this correction with the glasses may be, is ordered.\\nOccasionally the strength of the cylinder as well as its axis\\nis also changed.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0232.jp2"}, "233": {"fulltext": "HOW TO REFRACT. 22 5\\nObjections to the Postcycloplegic Method. The pa-\\ntient is annoyed by the long delay to which he is subjected\\nbefore getting his glasses. But the principal fault lies in\\nthe fact that the eye is not placed in the emmetropic condi-\\ntion it is allowed to retain more or less of its accommo-\\ndative power for distance. This, however, can not always\\nbe avoided.\\nStatic Refraction. By this method the glasses are pre-\\nscribed while the ciliary muscle is under the effect of the\\ncycloplegic. In hyperopia allowance must be made in the\\nstrength of the sphere for the distance at which the test is\\nmade. At 6 meters 0.25 is deducted from the sphere\\nwithout any change in the cylinder. The only possible\\nobjection to this method is in cases of hyperopia, in which,\\nafter the effect of the cycloplegic passes away, the ciliary\\nmuscle may endeavor to accommodate for distance with\\nthe glasses in position, and with the result that the pa-\\ntient can not see clearly except near at hand. To avoid\\nany such contingency the surgeon will have to make a\\ndeduction in the strength of the plus sphere to meet such\\ncases. The rule for ordering glasses by the static refrac-\\ntion in hyperopia is to deduct 0.25 from the sphere and\\nhave the glasses worn at once and constantly while the\\neffect of the drops is gradually leaving the eyes. In\\nthis way the eyes grow accustomed (slowly) to seeing at a\\ndistance without exerting the ciliary muscle the eyes are\\nthus placed in an emmetropic condition. If this effect of\\nthe cycloplegic passes away before the patient can obtain\\nthe glasses, it will be necessary to use the drops for a day\\nor so after the glasses are received. Unfortunately, how-\\never, some hyperopic eyes, in young subjects especially,\\nwith vigorous ciliary muscles, will develop a spasm of the\\naccommodation for distant vision which will make the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0233.jp2"}, "234": {"fulltext": "226 REFRACTION AND HOW TO REFRACT.\\nglasses very annoying on account of distant objects look-\\ning dim. Such patients should be advised of this fact\\nat the time the glasses are ordered, and if dim distant\\nvision does develop, that it will be transitory, and to per-\\nsist in wearing the glasses. There are two ways of reliev-\\ning this dim vision if it should occur\\n1. To prescribe a weak solution of atropin of a grain\\nto i fluidounce), I drop in each eye once or twice a day,\\nthe idea being to slightly relax the accommodation this is\\naccomplished, but, unfortunately, the mydriatic effect is a\\ndisturbing element which the patient will not submit to\\nlong enough, as a rule, to obtain relief.\\n2. The better way is to make a compromise in the\\nstrength of the sphere. An eye which has been in the habit\\nof accommodating 3, 4, 5, or 6 diopters for distance, does\\nnot often give up this habit veiy gracefully, even if assisted\\nby a slowly acting cycloplegic, so that when the static\\nrefraction calls for more than 3 diopters, the surgeon is fre-\\nquently compelled to make a deduction of more than 0.25.\\nThere is no hard and fast rule as to jtist hozu much shall be\\ndeducted, and very few surgeons agree on this point.\\nGlasses may be ordered as follows, the surgeon being\\nguided in great part by the patient s age and occupation\\nalso as to whether there is esophoria or exophoria. It\\nwill be found that cases of esophoria will accept almost\\na full correction, whereas cases of exophoria will require a\\nvery liberal deduction in the strength of the glass, the\\npatient being allowed to use his relative hyperopia\\nStatic refraction at 6 meters\\n-(-1. 00 sph. or less deduct 0.12 or 0.25.\\nFrom -j-1.00 sph. up to 3.00 sph. 0.25 or 0.50 or 0.75.\\n+3-00 sph. up to 6.00 sph. 0.50 or 0.75 or 1.00 or 1. 50.\\n-(-6.00 sph. up to 8.00 and above 1. or 1.50 or 2.00 up to 3.00.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0234.jp2"}, "235": {"fulltext": "HOW TO REFRACT. 227\\nIt is true that glasses ordered in this way do not leave\\nthe eyes in an emmetropic condition, and that, later on, when\\nasthenopic symptoms redevelop, the strength of the glasses\\nwill have to be increased. But this method has two advan-\\ntages first, it gives the patient his glasses without any long\\ndelay, and the eyes have an opportunity to become accus-\\ntomed to them while the effect of the drops is passing\\naway and, second, the patient accepts a much stronger\\nglass in this way than by the postcycloplegic method, which\\nis a decided advantage.\\nThe ordering of lenses in low errors for distant vi-\\nsion depends entirely upon the condition of the patient s\\neyes and symptoms. It is not unusual to find the most\\ndistressing asthenopia, headaches, blepharitis, etc., disap-\\npear as if by magic when corrections are ordered for small\\ndefects, especially if there is astigmatism. In other instances\\nslight ametropic errors may not produce any unpleasant\\nsymptoms, and such a patient need not wear the correction\\nfor distance.\\nThe Ordering of Glasses in Myopia. There is no\\nfixed rule for prescribing glasses in myopia. Each case is a\\nlaw unto itself, and should receive the most careful consid-\\neration from every point of view. But as the student must\\nhave some idea as to how to proceed, the writer would sug-\\ngest the following subdivisions\\nT. Myopic eyes which can with safety use one pair of\\nglasses for distant and near vision.\\n2. Myopic eyes which require two pairs of glasses one\\nfor distant vision, and another pair for near-work, reading,\\nwriting, etc.\\n3. Myopic eyes which should have the near correction\\nonly.\\nClass i comprises those cases in which there is an active", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0235.jp2"}, "236": {"fulltext": "228 REFRACTION AND HOW TO REFRACT.\\nciliary muscle, and the ophthalmoscope shows but little, if\\nany, change in the eye-ground indicative of stretching (chil-\\ndren, or in beginning myopia). Glasses carefully selected\\nby the static refraction may be ordered in such instances\\nfor constant use, but with the distinct understanding that\\nif any discomfort arises at any time they will be subject\\nto change.\\nClass 2. Adults who have not previously worn their\\nmyopic glasses. In these cases the power of the ciliary\\nmuscle is weak, deficient in sphincter fibers, and, if forced\\ninto activity, the patient would be very uncomfortable, the\\neye would stretch, and the myopia increase, the tissues in\\nthese eyes yielding more readily than in class 1. The\\nglasses selected by the static refraction may be prescribed for\\ndistance, but a second pair, 1, 2, or 3 diopters weaker, must\\nbe ordered for the reading, writing, or working distance,\\nthat the accommodative effort may in part be kept in\\nabeyance. Class 1, if not carefully watched, may pass\\ninto class 2 and class 2 may pass into class 3.\\nClass 3. These cases require unusually strong lenses,\\nand it is to these especially that the term sick, or\\nstretched eye particularly belongs. The ophthalmo-\\nscope may show vitreous opacities, areas of retinochoroid-\\nitis, macular choroiditis, a broad myopic conus, and even\\nposterior staphyloma. The eyes are prominent, occupying\\nmuch of the orbital space. Eyes of such length are limited\\nin their power of comfortable rotation, and hence it is com-\\nmon for one eye to diverge, the patient stating that he uses\\nonly one eye for near vision. The diverging eye is usually\\nmore or less amblyopic, due to want of use or pathologic\\nchanges, or to both. Such eyes have lost almost or quite\\nall the power of accommodation. These eyes must be\\nplaced in such a condition that the desire to converge and", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0236.jp2"}, "237": {"fulltext": "HOW TO REFRACT. 229\\naccommodate is at a minimum. The prescribing of glasses\\nfor these long eyes must be limited to the one pair for near-\\nwork, and yet the patient may, by bringing the glasses\\ncloser to the eyes, improve the distant vision for the time\\nbeing a sort of artificial accommodation. To appreciate\\nwhat is meant by this statement it is necessary to reconsider\\nthe optics of a myopic eye. A myopic eye of 20 D. has a\\nfar point of 5 cm., and the minus lens required to make\\nsuch an eye receive parallel rays of light at a focus upon\\nits retina should be of such strength that the rays passing\\nthrough it would have a divergence as if they came from\\nthis far point (5 cm.). Such a lens would be a 20 D.\\nThis means, of course, that the 20 D. would have to be\\nplaced with its surface against the surface of the cornea,\\nwhich is an impossibility. The usual distance for a lens in\\nfront of the eye is 1 or 1 J^ cm., so that this distance must\\nbe subtracted from the distance of the far point. In this\\ninstance 1 cm. from 5 cm. would leave 4 cm., and this would\\nrepresent 25 D. As just stated, the glasses for this class\\nof patients are limited to the one pair for near-work, and\\ntherefore it would be necessary to reduce the strength of\\nthese lenses 4 diopters and thus prevent, as far as possi-\\nble, any accommodative effort. The patient using this*\\n21 D. for near, can, if he wishes, improve his distant\\nvision at any time by pressing the lenses closer to his eyes.\\nThe strength of concave lenses increases as they are\\nbrought closer to the eyes, and diminishes as they are re-\\nmoved from the eyes.\\nCaution. The great danger in any refraction at the trial-\\ncase, but especially in myopia, is an overcorrection, and\\nthis is very likely to occur if the surgeon is not extraor-\\ndinarily careful in having his lenses placed as close to the\\neyes as possible while making the test.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0237.jp2"}, "238": {"fulltext": "23O REFRACTION AND HOW TO REFRACT.\\nProphylaxis. The prescribing of glasses for myopic\\neyes is only a part of the general treatment to which these\\nsick eyes are entitled. If the treatment stops at this\\npoint, then the glasses may be an injury instead of a bless-\\ning. Myopia once established may pass through the\\nvarious classes already described, and eventuate in greatly\\nreduced vision or total blindness if certain limitation of\\ntheir use is not insisted upon.\\n1. Light. A good, clear, and steady light is always essen-\\ntial it should come from the left side, never from in front.\\n2. Time. The length of time that myopic eyes may be\\nused should be restricted as much as possible, consistent\\nwith their condition that is to say, they should never be\\nused after they become the least fatigued, and any use of\\nthe eyes should be counteracted by life in the open air.\\n3. Attitudes. The head should have as little inclination\\nas possible in reading, writing, or close work, as so faulty a\\nposition invites a congestion of the intraocular tissues. At\\nschool or at home the book should be inclined, and its dis-\\ntance from the eyes be regulated by the size of the patient.\\n4. Print. The use of small print or minute objects\\nmust be forbidden. English or Gothic type should be sub-\\nstituted for Greek, German, and other characters. Fine\\nneedle-work, embroidery, etc., must be abolished. If nec-\\nessary, music notes must be given up entirely.\\n5. Health. The health of the patient must be looked\\nafter, and all irregularities corrected constipation, etc.\\nThese are a few of the major considerations to which the\\npatient s attention must be drawn, the surgeon being limited\\nin his remarks to the exigencies of the individual case.\\nIn conclusion it may be well to know how myopia is\\nproduced, since it has been stated that the condition is rarely\\nseen in young children. It is well known that astigmatism", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0238.jp2"}, "239": {"fulltext": "HOW TO REFRACT. 23 I\\n(hyperopic) is a congenital defect, and with this in mind it\\nis very easy to appreciate the succeeding steps which lead\\nto the compound myopic condition, showing at the same\\ntime the reason why simple myopia is so rare an anomaly.\\nTake a child six years of age who has a compound hyper-\\nopia of say +0.50 sph. O +0.75 cyl. axis 90 degrees this\\nchild enters upon its course of study without any correcting\\nglasses, and is subjected in its pursuit for knowledge to a\\nfaulty school desk and chair, possibly facing a window.\\nThe print is defective in many ways. The artificial light\\nfor home study in the evening may be of poor quality, and\\nso placed that but few of its rays fall upon the child s book.\\nWith these and other hindrances the eyes are strained\\n(stretched). The tissues are very yielding in their growing\\nstate, so that at the age of ten years the refraction may\\nshow +0.75 cyl. axis 90. The +0.50 sph. (the axial\\nametropia) has disappeared by an elongation of the optic\\naxis. The vertical meridian is now emmetropic. The same\\nconditions exist for the next three years, during which the\\nnumber of studies is multiplied and the hours for study are\\nprolonged and the child reaches the age of puberty the\\nrefraction is now found to be p. 50 sph. O +0.75 cyl.\\naxis 90 degrees, mixed astigmatism. In two years more the\\nrefraction is found to be 0.25 sph. O 0.75 cyl. axis\\n180 i. e. t compound myopic astigmatism. From this time\\nforward these eyes progressively stretch and are subject to\\nthe stretching process unless the progress is stayed with\\nglasses and prophylactic treatment.\\nIn the brief detail of this one case the student will fully\\nappreciate another important fact that the vertical meridian\\nof the cornea, as a rule, maintains throughout the shortest\\nradius of curvature. This is abundantly demonstrated by\\nstatistics.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0239.jp2"}, "240": {"fulltext": "232 REFRACTION AND HOW TO REFRACT.\\nThe following summary of refractive errors and direction\\nof meridians of shortest radius of curvature in 2500 pairs\\nof eyes, 1300 in private and 1200 in hospital work, pre-\\npared by Dr. Risley and the writer, shows the correctness\\nof the above statements\\nPrivate. Hospital.\\nMonocular astigmatism, 70 S-\u00c2\u00b0% 94 7-8%\\nBinocular astigmatism, 1 151 88.5 828 69.0\\nTotal cases, 1300 1200\\nBinocular symmetric astigmatism, 694 60.2% 613 74.4%\\nBinocular asymmetric astigmatism, 310 26.8 158 19.8\\nHeteronymous astigmatism, 123 10.6 40 5.2\\nHomonymous astigmatism, 24 2.1 17 1.2\\nTotal binocular astigmatism, 1151 828\\nSymmetric astigmatism\\n(a) According to rule (homologous), 543 78.2% 559 97.7%\\n(b) Against rule (heterologous), 151 21.8 54 2.3\\nTotal symmetric astigmatism, 694 613\\nAsymmetric astigmatism\\n(a) According to rule, 223 71.8% 126 79.1%\\n(b) Against rule, 87 28.2 32 20.9\\nTotal asymmetric astigmatism, 310 158\\nDirection of the Meridian of Shortest Radius in all Cases of\\nSymmetric Astigmatism.\\nMeridian at 90 57.0+%\\nMeridian inclined 1 5\u00c2\u00b0 or less on each side, J 9-7\\nMeridian inclined from 15 to 30 on each side, 4.0\\nMeridian inclined from 30 to 45 on each side, 1.0\\nMeridian at 180 to o\u00c2\u00b0 on each side, 12.0\\nMeridian inclined 15 or less on each side, 4.0\\nMeridian inclined from 15 to 30 on each side, 2.0\\nMeridian inclined from 30 to 45 on each side, 0.5\\nThis report was read in the Section on Ophthalmology at the forty-sixth\\nannual meeting of the American Medical Association, at Baltimore, Md., May\\n7 to 10, 1895.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0240.jp2"}, "241": {"fulltext": "CHAPTER X.\\nAPPLIED REFRACTION.\\nIn estimating the refraction of any eye the surgeon will\\ndo good work if he will make it a rule never to be satisfied\\nuntil each eye has a vision of or more, and if this visual\\nacuity is not attained, to understand the reason why\\nwhether it is his fault or the fault of the eye itself. It is\\nmost essential in every instance to have the good-will of\\nthe patient.\\nThe following cases are detailed so as to demonstrate\\neach form of ametropia in all its phases\\nCase I. Simple Hyperopia. This is a common form\\nof ametropia, occurring about 20 times in 100 cases\\nJanuary 3, 1899. John Smith. Age, twenty. Single. Stenographer.\\nO. D. p. p. type 0.50 D. at 14 cm.\\nO. S. p. p.= type 0.50 D. at 14 cm.\\nAdd.\u00e2\u0080\u0094 22 degrees abd.= 6 degrees.\\nHistory. Frontotemporal headaches almost constantly,\\nbut much worse when using eyes at near-work. Had\\nsevere headaches when a school-boy. Never liked to\\nstudy preferred out-of-door sports.\\nvS. P. Face symmetric, but narrow. Blepharitis mar-\\nginalis. Irises blue. Pupils round, 3 mm. in diam. Eyes\\nfix under cover.\\nOphthalmometer. Negative.\\nOphthalmoscope. Both eyes the same. Media clear.\\n20 2 33", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0241.jp2"}, "242": {"fulltext": "234 REFRACTION AND HOW TO REFRACT.\\nDisc small and round, with physiologic cup. All vessels\\nnear the disc are seen clearly with +3 S. Eye-ground\\nflannel-red and accommodation very active.\\nManifest or dynamic refraction\\nO.D.+i.2 S S.=^-.\\nO. S. 4-1.25 S.=\\nBe Atropin and dark glasses for refraction.\\nJanuary 5, 1899. Patient seated at 6 meters from test-\\ncard and small point of light. O. D. V.= ^y O. S.\\nV. x^. Cobalt-blue glass shows (each eye separately)\\nblue center and red halo. (See Fig. 118.)\\nRetinoscope, with -f-4 S., developed point of reversal at\\n1 meter for each eye.\\nWith trial -lenses, O. D. and O. S. each select +3 S.,\\nwhich gives a vision of -y-- t and they positively refuse to\\nsee clearly with an addition of +0.25 S. In other\\nwords, this -f- 3 S. is the strongest lens which each eye will\\naccept and maintain clear distant vision. The rule for\\nrefraction in Jiyperopia is to employ the strongest lens\\nwhich the eye will accept without blurring the distant\\nvision.\\nTo prove that the ciliary muscle is at rest, and that the\\nglass selected is correct, add a -(-4 S. to the distance cor-\\nrection, and the rays of light emerging from the eye must\\nfocus at the principal focus of the added +4 S., at 10\\ninches (25 cm.) and if the patient can read fine print at\\nthis distance, the ciliary muscle is at rest and the glass cor-\\nrect. If a +3 S. had been added instead of a +4 S., then\\nthe principal focus would be at 13 inches; if +5 S., then\\nat 8 inches, etc.\\nThe question is, What glasses shall be ordered The", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0242.jp2"}, "243": {"fulltext": "APPLIED REFRACTION. 235\\nwriter would give the following prescription, and instruct the\\npatient to stop the drops and wear the glasses constantly\\nFor Mr. Smith.\\nR. O. D. +2.75 sph.\\nO. S.-ft 2.75 sph.\\nSig. For constant use.\\nJanuary 7, 1899.\\nJanuary 8th Glasses from the optician neutralize are\\ncentered and accurately adjusted.\\nJanuary 21st Add. 18 degrees. Abd. 6 degrees.\\nNear point in each eye 10 cm. No headache or dis-\\ncomfort of any kind.\\nConsiderations. The static refraction as represented by\\n3.00 sph. means that rays of light which pass through\\nthis lens and focus at the fovea diverge from six meters\\ndistance, which heretofore we have considered for purposes\\nof calculation as parallel but when glasses are ordered,\\nallowance must always be made for this small amount of\\ndivergence, and so 0.25 is deducted from the +3 sph., that\\nthe eye may have parallel rays focusing on its retina when\\nlooking beyond a distance of six meters. To have been\\nmathematically exact, +0.12 should have been deducted in\\nplace of +0.25.\\nThe purpose in all cases of refraction is to place the eye\\nin an emmetropic condition, though this is not always advis-\\nable in every instance. The hyperopic eye naturally accom-\\nmodates for distance, and the emmetropic eye does not then\\nthe hyperopic eye is made emmetropic when a spheric lens\\npermits parallel rays to focus upon its fovea without any\\nassistance whatever from the ciliary muscle.\\nAdvantages of Atropin in This and Similar Cases.\\nThe glasses are ordered while the ciliary muscle is at rest.\\nThe accommodation returns gradually. The eye becomes", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0243.jp2"}, "244": {"fulltext": "236 REFRACTION AND HOW TO REFRACT.\\naccustomed to seeing at a distance without the assistance\\nof the ciliary muscle. Atropin produces a physiologic rest,\\nwhich the overacting ciliary muscle, disturbed choroid, and\\nirritated retina require. None of these good results can be\\nexpected in a case of this kind from the use of a quick\\ncycloplegic like homatropin.\\nSummary. Age of patient, twenty years. Amplitude of\\naccommodation is 10 D. for this age.\\nNear point is 14 cm., which shows only 7 D.\\nFacultative hyperopia (Hf.) equals difference between 10\\nand 7 D., which is 3 D.\\nManifest hyperopia (Hm.j equals 1.25 D.\\nTotal hyperopia, or static refraction (Ht), equals 3 D.\\nLatent hyperopia (HI.) equals the difference between the\\nmanifest and total, 3 D. and 1.25 D., making 1.75 D.\\nThe far point, or conjugate focus, is negative or virtual,\\nand lies back of the retina, where the emergent rays (diverg-\\ning) from the eye would meet if projected backward this\\npoint corresponds to the principal focus of the lens which\\ncorrects the hyperopia i. e., in this instance, +3 D., and\\nthe negative far point is therefore at 1 3 inches.\\nThe +2.75 makes the eye practically emmetropic; the\\nnear point, after the effect of the atropin passes away, is 1 o\\ncm., which is the emmetropic near point for the patient s\\nage. The plus sphere selected represents a shortening of\\nthe eye of 1 mm., as measured on the optic axis.\\nCase II. Simple Myopia. With the one exception of\\nemmetropia, it will be found that myopia, plain and simple,\\nwithout astigmatism, is one of the rarest conditions of the\\neye which the surgeon will meet in careful refractive work.\\nAbout one and one-half per cent, of all patients, by careful\\nrefraction, are found to have simple myopia. Therefore\\nthe condition is not common.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0244.jp2"}, "245": {"fulltext": "APPLIED REFRACTION. 237\\nJanuary 3, 1899. Miss Rare. Age, twenty-five years. Single.\\nO. D. V. p. p. =type 0.50 D. at 9 cm.; p. r. at 33 cm.\\nO. S. V. -=y-. p. p. type 0.50 D. at 9 cm.; p. r. at 33 cm.\\nAdd. 16 degrees. Abd. 6 degrees. Exophoria, 3 degrees at 13 inches.\\nHistory. Does not suffer much from headache, but eyes\\nache after any prolonged use at near-work. Never able to\\nsee well at a distance. Always stood high in her class at\\nschool, though she had to have a front seat to see the fig-\\nures and writing on the blackboard. Has excellent vision\\nfor near-work and does fine embroidery. Has been accused\\nof passing friends on the street without speaking to them.\\nIf she drops a pin on the floor, has to get on her knees to\\nfind it. Parents do not wear glasses. Grandfather had\\nelegant sight, had second sight, and never wore\\nglasses. Patient has postponed getting glasses because\\nparents objected.\\n5. P. Face symmetric. Interpupillary distance, 65 mm.\\nIrises dark. Pupils large, round, 5 mm. Eyes out under\\ncover.\\nOphthalmometer. Negative.\\nOphthalmoscope shows each eye the same. Media clear.\\nDisc large and round. Shallow physiologic cup. Narrow\\nmyopic conus at temporal side of disc. Choroidal vessels\\nseen throughout periphery of eye-ground and extending\\nalmost to nerve margin. All vessels near nerve-head seen\\nwith 3. S.\\nManifest Refraction. Each eye 3.50 sph. gives vision\\nr VI\\nof vr\\nCobalt-blue glass gives red center and dark blue halo.\\n(See Fig. 119.)\\nR. Atropin and dark glasses for refraction.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0245.jp2"}, "246": {"fulltext": "238 REFRACTION AND HOW TO REFRACT.\\nJanuary 5, 1899: Patient seated at 6 meters from test-\\ncard. O. D. and O. S. vision equals Retinoscope with\\n2. S. develops point of reversal at 1 meter for each eye.\\nIt will be noticed that the vision in hyperopia with and\\nwithout drops is decidedly different, whereas in myopia\\nthere is little, if any, change. With trial-lenses each eye\\nselects separately 3 sph., which gives a vision of If a\\n2.75 sph. is substituted, the vision falls to r^gg. If a.\\n3.25 is employed, the vision remains but the letters\\nlook small, black, and far away. The rule for refraction\\nin myopia is to employ the weakest lens through which the\\neye can still maintain clear, distant vision.\\nWhat Glass to Order. The writer would give the fol-\\nlowing prescription and instruct the patient to stop the\\ndrops and wear the glasses constantly\\nJanuary 7, 1899. For Miss Rare.\\nR. O. D. \u00e2\u0080\u00943.00 sph.\\nO. S. 3.00 sph.\\nSlG. For constant use.\\nJanuary 9th Glasses neutralize are centered and accu-\\nrately adjusted. Add. 18 degrees. Abd. 10 degrees.\\nPatient is delighted with glasses.\\nJanuary 21st: Near point, 12 cm.\\nConsiderations. As a rule, concave lenses are ordered\\nwithout any deductions for the slight amount of diver-\\ngence of the rays of light for the distance (6 meters) at\\nwhich the estimate is made. To be exact, 0.25 should\\nbe added to the 3.00 sph. in this case but the surgeon\\nmust avoid the danger of twrcorrecting the myopic eye,\\nand, to be on the safe side, the glass is usually ordered as the\\npatient selects and the retinoscope confirms it. These lenses\\nmake the eyes, to all intents and purposes, emmetropic.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0246.jp2"}, "247": {"fulltext": "APPLIED REFRACTION. 239\\nAdvantages of Atropin.\u00e2\u0080\u0094 The choroid and retina are\\ngiven a physiologic rest that they could not obtain in any\\nother way. The patient will not select too strong a glass,\\nas was the case in this very instance when manifested.\\nMyopic eyes usually have large pupils, and do not suffer,\\ntherefore, from mydriasis to the same extent as hyperopic\\neyes. The far point remains unchanged. The power of con-\\nvergence is somewhat relieved by the glasses, which at\\nthe near working distance are of the nature of prisms,\\nbases in.\\nSummary. Age of patient is twenty-five years. Ampli-\\ntude of accommodation at this age is 8 D. Near point, 9\\ncm. 1 1 D., and far point 33 cm. 3 D. Difference be-\\ntween near point and far point in diopters =8 D., which is\\nthe amplitude of accommodation for the patient s age.\\nDifference between the near point in diopters (11 D.)\\nand the amplitude (8 D.) is 3 D., which is the amount of\\nthe distant correction needed. With glasses on, the near\\npoint, after the effect of the atropin passes away, is 12 cm.,\\nwhich represents the emmetropic near point for the age.\\nThis myopia of 3 D. represents an eye 1 mm. longer than\\nthe standard eye, as measured on the optic axis.\\nCase III. Simple Hyperopic Astigmatism. Not an\\nuncommon condition. About 5.5 percent, of all eyes have\\nthis form of refraction.\\nApril 3, 1899. Miss Robinson. Age, twenty-four years. Single. Dress-\\nmaker.\\nVi\\nO. D. V.=-|jr? p. p. type 0.50 at 18 cm.\\nVI\\no. s. v. ~ix p- p- typ 6 \u00c2\u00b0-5\u00c2\u00b0 at J 8 cm\\nAdd., 23 degrees. Abd., 5 degrees. At 6 meters, esophoria 4 degrees\\nat 13 inches, I degree of esophoria.\\nAstigmatic clock-dial shows darkest lines from X to\\nIV with O. D.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0247.jp2"}, "248": {"fulltext": "240 REFRACTION AND HOW TO REFRACT.\\nAstigmatic clock-dial shows darkest lines from VIII to\\nII with O. S.\\nHistory. Headache every day seldom entirely free from\\nocular discomfort. Distress begins in the forehead and\\nextends to the back of the head and into the neck. After\\na hard day s sewing, has to go to bed and bind the head\\nwith a handkerchief. Once a week has a sick headache,\\nwhen she has to give up work entirely and take headache\\npowders. Sick headache often ceases after emesis.\\n5. P. Face symmetric. Blepharitis well marked, with\\nmany cilia missing. Edges of lids thickened. Irises light\\nblue in color. Pupils apparently oval in vertical meridian.\\nCorneal reflex shows axis inclined from vertical in each eye.\\nOphthalmometer. O. D., 3.50 axis, 75, with the rule\\nO. S., 3.50; axis 105 degrees, with the rule.\\nOplitlialmoscope. O. D., vertically oval nerve axis, 75\\ndegrees. Accommodation very active. Underlying conus\\ndown and out. Vessels at 75 best seen with 2. 50 and at\\naxis 165, without any lens. O. S., same general conditions\\nas in O. D. Vertically oval nerve axis, 105. Vessels at 105\\ndegrees seen with +2.50, and at axis 15 without any lens.\\nManifest Refraction.\\nVI\\nO. D., +2.50 cyl. axis 65 degrees -yj-\\nO. S., same cylinder with axis 125 degrees.\\nR Hyoscyamin and dark glasses for refraction.\\nApril 5 th Six meters from test-card and point of light.\\nO. D. v.\\nO. S. V.\\nClock-dial shows the same as at first examination.\\nCobalt-blue glass before O. D. gives blue center and red\\non each side at axis 165 degrees. O. S. the same at axis\\n15 degrees. (See Fig. 121.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0248.jp2"}, "249": {"fulltext": "APPLIED REFRACTION. 241\\nStenopeic Slit. O. D., axis 75 with +0.25 S., V.\\nand at axis 165 with -f 2.50 S., V. O. S., axis 105\\nwith +0.25 S., V. -^j- and at axis 15 with +2.50 S.,\\nV.\\nVI\\nRetinoscope at 1 meter shows O. D., at axis 75 degrees\\n-j-1.25 S., and axis 165 degrees, 4- 4. 2 5 S. O. S., at axis\\n105 degrees, -f-1.25 and at axis 15 degrees, +4.25 S.\\nAt Trial- case.\\nO. D. \u00e2\u0080\u00940.25 sph. O +3.00 cyl. axis 75 degrees, V. -f-\\nO. S. \u00e2\u0080\u00940.25 sph. O -p3.oo cyl. axis 105 degrees, V. _*\u00c2\u00a3 -j-.\\nApril 6th Same result as April 5th. Add., 20 degrees.\\nAbd., 6 degrees. Esophoria, 2 degrees at 6 meters.\\nFor Miss Robinson.\\nR. O. D. \u00e2\u0080\u00943.00 cyl. axis 75 degrees.\\nO. S. -r3.oo cyl. axis 105 degrees.\\nSlG. For constant use.\\nApril 7th Glasses neutralize are centered and accu-\\nrately adjusted.\\nApril 1 6th Perfectly comfortable. Free from headache\\nsince the first day she used the drops. Add., 20 de-\\ngrees. Abd., 6 degrees. Esophoria at 6 meters, 2 de-\\ngrees and at 13 inches, o\u00c2\u00b0. Near point, 12 cm.\\nConsiderations. Apparently, the static refraction in this\\ncase would indicate compound hyperopic astigmatism but\\nwhen 0.25 is deducted to produce parallel rays, then the\\nprescription becomes one for simple hyperopic astigmatism.\\nGeneral Rule for Prescribing Cylinders. Order the\\ncylinder just as found, without any change in its axis or\\nstrength.\\nThe vision in each eye at the different visits, before\\nlenses were placed in front of the eyes, was always uncertain,\\n21", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0249.jp2"}, "250": {"fulltext": "242 REFRACTION AND HOW TO REFRACT.\\nthe patient miscalling certain letters, and hence it is that\\nthe vision is recorded with as many question marks as\\nthere are mistakes in the line of letters i. e.\\nIn taking the vision at the first visit, the patient could\\nread part of tfj^ if not closely watched. In other words,\\nif she was permitted to tilt her head to one side and nar-\\nrow the palpebral fissure by squinting the lids together, and\\nmaking, as it were, a stenopeic slit out of her eyelids, the\\nvision was improved. But when told to open the eye wide,\\nshe could read only part of -y^-. This is explained by\\nthe fact that when the lids were drawn together, the verti-\\ncal meridian was partly excluded, and then, by accommo-\\ndating, the vision was improved through the horizontal\\nmeridian. Astigmatic eyes often take advantage of this\\ncondition when the nature of the astigmatism is suitable,\\nbut only at the expense of frowning and straining the\\naccommodation.\\nIt will also be noticed that the stenopeic slit was not used\\nas a test at the first visit. This is also explained for the\\nsame reason that the patient would draw his lids together\\nand therefore annul the virtue of this test. The stenopeic\\nslit is to be used in these cases only when the ciliary muscle\\nis at rest.\\nSummary. When the hyoscyamin has passed out of\\nthe eyes and the glasses are in position, the near point be-\\ncomes 12 cm., which is quite consistent with the patient s\\nage. Before using drops, the near point with the eyes wide\\nopen was only 18 cm., representing about 5.50 D. and\\nthis, subtracted from the amplitude for twenty -four years of\\nage, would leave 3 D. for distance uncorrected.\\nAs every 6 D. cylinder represents 1 mm. of lengthening\\nor shortening of the radius of curvature of the cornea,\\nthen this patient, taking a 3 cyl. at axis 7 5 in the right", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0250.jp2"}, "251": {"fulltext": "APPLIED REFRACTION. 243\\neye, has the 165 degree meridian y 2 of a mm. too long as\\ncompared with the 75 meridian, which is supposed to have\\nthe normal radius of 7.8 mm.\\nThe same is true of the meridians of the left eye.\\nCase IV. Simple Myopic Astigmatism. Not a com-\\nmon condition. About 1.5 per cent, of all eyes have this\\nform of refraction..\\nSingle.\\ntil 10.\\nMiss\\nJenks.\\nAge,\\neighteen\\nyears.\\nO.\\nD.\\nV.\\np.\\np. 9 cm.\\nO.\\nS.\\nV.\\np.\\np. 9 cm.\\nAdd. 20 degrees. Abd., 5 degrees. Esophoria at 6 meters 3 degrees\\nand I degree at 13 inches.\\nPointed Line Test. Each eye selects the series of points\\nfrom XII to VI as coalescing and appearing as dark\\nlines.\\nCobalt-blue Glass. O. D. and O. S. each show blue\\nabove and below the red. (See Figs. 122 and 123.)\\nStenopeic Slit. Axis 90 degrees V. axis 1 80 V.\\nXL\\nvi\\nHistory. Never had good distant vision. Has occa-\\nsional headaches. Comes to find out if glasses will im-\\nprove vision.\\nvS. P. Face symmetric. Irises dark in color. Pupils\\napparently round, 4 mm. in diameter. Eyes out under\\ncover.\\nOphthalmometer. Each eye 2D., axis 90.\\nOphthalmoscope. O. D., media clear. Disc large and\\nround, with underlying conus out. No physiologic cupping.\\nChoroidal circulation everywhere recognized, characteristic\\nof a stretching eyeball. Horizontal vessels seen with\\n2 S. vertical vessels seen without any correcting lens.\\nO. S., same general conditions as in O. D.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0251.jp2"}, "252": {"fulltext": "244 REFRACTION AND HOW TO REFRACT.\\nManifest Refraction.\\nO. D., \u00e2\u0080\u00942.50 cyl. axis 180 -^rr.\\nO. S., 2.50 cyl. axis 180 ^-r-.\\nR Atropin and dark glasses for refraction.\\nApril 1 2th Six meters from test-card and point of light.\\nRetinoscopy at one meter. Vertical meridian +1.25 S.\\nHorizontal meridian 1.00 S.\\nStenopeic slit at axis 1 80 with +0.25 at axis 90\\nCobalt-blue glass and pointed line test show same results\\nas at first visit\\nVI\\nO. D. V.\\nO.S. V.=^???.\\nAt Trial -case.\\nVI\\nO. D., -fo.25sph. O 2.00 cyl. axis 180 degrees -yp\\nVI\\nO. S., +0.25 sph. 3 2 c yl\u00c2\u00ab ax i s 180 degrees ^ttj-.\\nApril 1 3th Same results as yesterday. Add. 20\\nAbd. 6. Esophoria, 2 degrees.\\nFor Miss Jenks.\\nJjc O. D., 2.00 cyl. axis 180\\nO. S., 2.00 cyl. axis 180.\\nApril 14th Glasses neutralize. Centered and properly\\nadjusted.\\nApril 28th Comfortable. Enjoys good distant vision.\\nNear point, each eye, 9 cm.\\nConsiderations. Apparently, the static refraction would\\nindicate mixed astigmatism, but when +0.25 is deducted\\nto produce parallel rays, the prescription resolves itself into\\none for simple myopic astigmatism.\\nThe general rule for ordering cylinders is the same in", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0252.jp2"}, "253": {"fulltext": "APPLIED REFRACTION. 245\\nmyopia as in hyperopia i. e., no change in the strength or\\nin the axis of the cylinder.\\nA cycloplegic is always necessary in such cases, as is\\nshown by the different results obtained by the manifest and\\nstenopeic slit.\\nThe vision was always uncertain before lenses were placed\\nbefore the eyes, as is indicated by the question marks.\\nAt the first visit the vision was taken with the eyes wide\\nopen. If allowed to narrow the palpebral fissure by squint-\\ning the eyelids together and making a stenopeic slit out of\\nthem, the patient could read a part of ^^s When the\\nlids were thus drawn together, the myopic vertical meridian\\nwas excluded in part and the horizontal meridian was util-\\nized. The stenopeic slit was of some assistance before\\ndrops were used, as the accommodation could not be\\nexerted, as in the case of the hyperope.\\nSummary. After recovery from the cycloplegic, small\\ntype was clear at 9 cm., which was in keeping with the\\npatient s age. The near point before drops were used\\nwas also 9 cm., but not constant, nor was the type clear.\\nThe 2.00 cyl. at axis 180 represents y^ of a mm. of\\nshortening in the vertical radius of curvature as compared\\nwith the normal radius of 7.8 mm. in the horizontal.\\nThe astigmatism is regular, symmetric, with the rule.\\nCase V. Compound Hyperopic Astigmatism. The\\nmost common form of all refraction. It is a combination\\nof simple hyperopia with simple hyperopic astigmatism.\\nAbout 44 per cent, of all eyes have this form of refraction.\\nApril 1 2th. Mr. Common. Age, twenty-eight. Married. Bookkeeper.\\nVI\\nO. D. V. p. p. type 0.75 D. 22 cm.\\nO. S. V. p. p. type 0.75 D. 22 cm.\\nAdd., 23 degrees. Abd., 7 degrees. Esophoria, 2 degrees; at 13\\ninches, o.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0253.jp2"}, "254": {"fulltext": "246 REFRACTION AND HOW TO REFRACT.\\nAstigmatic Clock-dial. O. D. and O. S. each selects\\ndarkest series of lines from IX to III.\\nPlacido s disc shows each corneal image as a horizontal\\noval. Scheiner s test shows two lights, separated in all\\nmeridians the vertical have the least separation and the\\nhorizontal the most.\\nOphthalmometer. 2.25 D. with axis 90 in each eye.\\nHistory. Family physician has tried in vain to stop the\\nheadaches, which he said were from biliousness. Headache\\ndevelops as soon as the patient commences to use his eyes,\\nand gets worse toward noon and from that time on, during\\nthe rest of the day, he is cross and irritable, and feels dizzy.\\nUnable to read in the evenings as he did a few years\\nago. Is wearing a pair of rest glasses, which he received\\nfrom an optician they were of some benefit for a very short\\ntime.\\n5. P. Lid margins red and excoriated. Many fine scales\\n(looking like dandruff) adhering to the cilia. Irises gray\\nin color. Pupils round, 3 mm. Eyes in, under cover.\\nOphthalmoscope. O. D. and O. S. each medium clear.\\nDisc small, vertically oval. Shallow physiologic cup.\\nVenous pulsation on disc. Narrow conus to temporal side.\\nNerve-head prominent and edges somewhat hazy. No path-\\nologic conditions recognized. Vertical vessels best seen\\nwith +3.00 and horizontal with -j- 1.00.\\nR Duboisin and dark glasses for refraction.\\nApril 14th: Six meters from test-card and point of light.\\nVI\\nO. D. V.\\nO. S.V.\\nRetinoscopy develops point of reversal at one meter in\\neach eye; vertical meridian with +2.25 S., and horizontal\\nmeridian with +4-00 S.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0254.jp2"}, "255": {"fulltext": "APPLIED REFRACTION. 247\\nStenopeic slit axis 90 degrees with +1.25 yj- at axis\\n180 degrees with +3- 00\\nCobalt-blue glass, blue center and red all round, more\\nconspicuous on the right and left sides. (See Figs. 124\\nand 125.)\\nAt Trial-case.\\nO. D., +1.25 sph. 3 4-1-75 cyl. axis 90 -rS-.\\nO. S., +1.25 sph. O -f 1.75 cyl. axis 90\\nApril 15th Same results as April 14th. Add., 22. Abd.,\\n7. Esophoria, 1 degree.\\nFor Mr. Common\\nR. O. D., -(-1. 00 sph. O +I-75 cyl. axis 90 degrees.\\nO. S., -|-i.-00 sph. O +1.75 cyl. axis 90\\nSlG. For constant use.\\nApril 17th: Glasses neutralize; are centered and ad-\\njusted.\\nApril 24th Has been perfectly free from headaches\\never since getting glasses. Never realized what a blessing\\nglasses could be. Near point with each eye is now 14 cm.\\nConsiderations. The prescription for glasses was the\\nsame as the static refraction, with the exception of the re-\\nduction in the strength of the sphere. No change in the\\ncylinder. A cycloplegic as a means of obtaining a prompt,\\ncorrect, and satisfactory result in such cases can not be dis-\\npensed with.\\nThe decided change in the vision before and with the\\ncycloplegic is quite diagnostic of compound hyperopic as-\\ntigmatism. When the cylinder and sphere are of any con-\\nsiderable strength, the patient can often overcome (faculta-\\ntive hyperopia) the spheric but not the cylindric correction.\\nSummary. After recovery from the cycloplegic the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0255.jp2"}, "256": {"fulltext": "248 REFRACTION AND HOW TO REFRACT.\\nsmall type becomes clear at about 13 cm., which is the\\nnear point consistent with the patient s age. The far point\\nbefore using drops was really two points, both negative\\nthat of the vertical meridian being about 1 meter, and the\\nhorizontal meridian about J^ of a meter back of the retina.\\nThe form of the astigmatism is regular, symmetric, and\\nwith the rule.\\nCase VI. Compound Myopic Astigmatism. A com-\\nbination of simple myopia with simple myopic astigmatism.\\nThis is the usual form of refraction in myopic eyes. About 8\\nper cent, of all eyes have compound myopia. The writer s\\nexperience is such that he never refracts a case of myopia\\nwithout searching carefully for a cylinder in combination\\nwith the sphere.\\nApril 1 2th. Mrs. Usual. Age, thirty years. Married. Housewife.\\nVI\\nO. D. V., -jj- type 0.50 7 to 14 cm.\\nVI\\nO. S. V., -j\u00e2\u0080\u0094 type 0.50 7 to 14 cm.\\nAdd., 16 degrees. Abd., 6 degrees. Exophoria at 6 meters, 2 degrees.\\nHistory. Suffers from ocular pains, as if knife -points\\nwere sticking into the eyes, which come on as soon as near-\\nwork is attempted or continued. Says that she constantly\\nsees fine dust particles floating before her vision. Has been\\nwearing glasses from an optician 3 sph.). Has all the\\nsymptoms of near-sightedness. Family history of father\\nand two sisters wearing glasses for near sight.\\n5. P. Face symmetric. Eyeballs prominent. Irises\\ndark in color. Pupils small (for a myope) and round,\\n3 mm. Eyes markedly out under cover.\\nOphthalmoscope. O. D., many fine floating vitreous\\nopacities. Nerve large and round, with broad underlying\\nconus down and out. Choroidal vessels seen throughout\\neye-ground. Vessels at about axis 120 degrees best seen", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0256.jp2"}, "257": {"fulltext": "APPLIED REFRACTION. 249\\nwith 2, and vessels at axis 30 degrees best seen with 3.\\nO. S., same general conditions as in O. D., except the prin-\\ncipal meridians are about 60 degrees and 150 degrees.\\nIndirect method shows a vertically oval nerve, with the\\nconus to the nasal side of the aerial image (as the eye-\\nground and nerve-head have undergone vertical and lateral\\ninversion). Withdrawing the lens, the nerve grows larger\\nin all meridians, but more so in the vertical.\\nCobalt-blue glass shows O. D. red center, blue all around,\\nmore pronounced on the sides in the 120 meridian. O. S.\\nshows red center, blue all around, more pronounced on the\\nsides in meridian of 60 degrees. (See Figs. 126 and 127.)\\nStenopeic slit before O. D. at axes 1 20 V. Y* at\\naxis 30 V. O. S., the same with axes 60 degrees\\nand 150 degrees.\\nAstigmatic Chart. O. D. selects the lines from V to XI\\nas darkest. O. S. selects the lines from VII to I as\\ndarkest.\\nOphthalmometer. O. D., 1 D., axis 35 degrees. O. S.,\\n1 D., axis 145 degrees.\\nManifest.\\nO. D. \u00e2\u0080\u00942. 50 sph. O o. 75, cyl. axis 35\\nO. S., 2.50 sph. O 0.75 cyl. axis 145 ^ff\\nR Atropin and dark glasses for rest and refraction.\\nApril 13th: At six meters from test-card and point of\\nlight\\nO.IXV. O.S.V.=^?.\\nO. D., 2.00, sph. O 1. 00 cyl. axis 30 -yj-\\nO. S., 2.00 sph. O 1. 00 cyl. axis 150 yf???.\\nRetinoscope confirms this trial -case result. Retinoscope\\nalso shows a general cloudiness of the media (vitreous),", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0257.jp2"}, "258": {"fulltext": "250 REFRACTION AND HOW TO REFRACT.\\nwhich, of course, will account in part for the vision not\\nbeing in each eye with correcting glasses.\\nApril 14th Same result as on the 13th.\\nFor Mrs. Usual.\\nR. O. D., 2.00 sph. O 1. 00 cyl. axis 30 degrees.\\nO. S., 2.00 sph. O 1. 00 cyl. axis 150\\nSig. For distance, as directed.\\nApril 15th:\\nR Tonics. Rest of eyes. Attention to general health.\\nApril 1 7th Glasses neutralize are centered and ad-\\njusted.\\nApril 29th Add., 16. Abd., 6. Exophoria, 2.\\nVision in each eye ^gg, read slowly.\\nConsiderations. The static refraction was ordered just\\nas found, and no deduction whatever was made in the\\nsphere. The rule is to prescribe in the same way as in\\nsimple myopia. But all cases of myopia can not and must\\nnot be prescribed for by rule. Each case of myopia is a\\nlaw unto itself. See description under General Considera-\\ntions, page 238, also pages 227, 228, and 229.\\nSummary. The near point is now 14 cm., which is\\nperfectly consistent with the patient s age. Fourteen centi-\\nmeters represents an accommodative power of 7 D., and\\nthis was the difference between the near and far points\\nbefore the drops were used. The astigmatism is regular,\\nsymmetric, and with the rule. Vision is not brought up to\\nnormal on account of the changes in the vitreous and dis-\\nturbed eye-ground, due, no doubt, to the want of a proper\\ncorrection the cylinder. The choroid and retina are both\\nin a stretching condition.\\nCase VII. Mixed Astigmatism. Not an uncommon\\ncondition. About 6yi per cent, of all eyes have this form", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0258.jp2"}, "259": {"fulltext": "APPLIED REFRACTION. 25 I\\nof refraction. This is a combination of the simple hyper-\\nopic and simple myopic astigmatisms, with their axes oppo-\\nsite or at right angles to each other, as a rule.\\nApril 8th. Mr. Crook. Age, twenty-one years. Single. Clerk.\\nVI\\nO. D. V. -j^. p. p. 14 cm. with type 0.75 D.\\nVI\\nO. S. V. -j\u00c2\u00a3L. p. p. 14 cm. with type 0.75 D.\\nAdd., 20. Abd., 10.\\nHistory of poor sight all his life, but thinks it was better\\nas a boy. Has frequent frontotemporal headaches, which\\nare worse after using eyes at any prolonged near-work.\\nFather has good sight, but his mother and her family have\\nall been near-sighted has one aunt that developed cata-\\nracts. Has been to several stores, but could not get\\nfitted with glasses that would improve his vision.\\nS. P. Face broad and symmetric. Long interpupillary\\ndistance. Irises dark in color. Pupils large, 5 mm.\\nround. Eyes out under cover.\\nOphthalmoscope. O. D., media clear. Disc vertically\\noval, axis 105. Macular region shows changes. Vessels\\nat 105 best seen with -\\\\-2, and at right angles with 2.\\nO. S., same conditions found, except that the meridians are\\nat 75 degrees and 165 degrees.\\nOphthalmometer. O. D., 4 D. axis 100. O. S., 4 D.\\naxis 75.\\nCobalt-blue Glass. O. D. violet center, blue above and\\nbelow in meridian of 105 and red at the sides in meridian\\nof 15. O. S., violet center, blue above and below in\\nmeridian of 75, and red on sides at axis 165. (See Figs.\\n128 and 129.)\\nStenopeic Slit. O. D. axis 15 with -\\\\-2 sph., V.=\\nat axis 105 with 2 sph., V. O. S. axis 165 with\\n2 sph., V\u00c2\u00bb=^r; at axis 75 with 2 sph., V.=", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0259.jp2"}, "260": {"fulltext": "252 REFRACTION AND HOW TO REFRACT.\\nIndirect Method. Each eye shows a lengthening of\\nthe vertical meridian as the condensing lens is withdrawn\\nfrom the eye, and at the same time the horizontal meridian\\ngrows narrower. As the lens is advanced toward the eye\\nthe vertical meridian grows shorter and the horizontal\\nmeridian grows broader.\\nThe ^astigmatic chart does not show any difference in the\\nshading of the lines they all appear about the same.\\nRetinoscope at 1 meter distance shows myopia in the verti-\\ncal meridian and hyperopia in the horizontal.\\nR Atropin and dark glasses for refraction.\\nApril 10th At six meters from test-card and point of\\nlight. O. D. and O. S. V.\\nCobalt-blue glass shows the same as at first visit.\\nRetinoscope at the distance of one meter shows point of\\nreversal in O. D. at axis 105 degrees with 1.50D., and\\naxis 15 with +3 D. O. S., axis 75 with 1.50 D., and\\naxis 165 with +3 D.\\nStenopeic Slit. O. D., axis 15 with +2 sph., V.\\naxis 105 with 2.50. sph., V. O. S., axis\\n165 with -\\\\-2 sph., V. at axis 75 with 2.50 sph.,\\nV\\nv IX\\nAt Trial-case. O. D 2.50 cyl. axis 15 degrees O\\n2 cyl. axis 105 degrees, V. O. S., 2.50 cyl.\\naxis 165 O+2 cyl. axis 75, V.\\nOr,\\nVI\\nO. D., \u00e2\u0080\u00942.50 sph. O -+4.50 cyl. axis 105, V. y^gg.\\nVI\\nO. S., \u00e2\u0080\u00942.50 sph. O +4.50 cyl. axis 75, V. yijgg.\\nOr,\\nVI\\nO. D. -f-2 sph. O 4.50 cyl. axis 15 degrees, V. yiiss\\nVI\\nO. S. -{-2 sph. O 4.50 cyl. axis 165, V. yjjgg", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0260.jp2"}, "261": {"fulltext": "APPLIED REFRACTION. 253\\nApril nth: Same results as April ioth. Add., 20.\\nAbd., 8.\\nFor Mr. Crook.\\nO. D. 4-2 sph. O 4.50 cyl. axis 15 degrees.\\nO. S. -f- 2 s P n 4-5\u00c2\u00b0 c yl- axls ^5\\nSlG. For constant use.\\nApril 1 2th Glasses neutralize are centered and adjusted.\\nApril 26th Near point 10 cm., which is consistent with\\nage of patient.\\nConsiderations. The ophthalmoscope, retinoscope,\\ncobalt-blue glass, indirect method, and stenopeic slit were\\ndirect guides to the character of the refractive error.\\nEmphasis is placed upon these different methods, as so many\\nbeginners in ophthalmology have a fear or dread of the re-\\nsult in refracting cases of mixed astigmatism.\\nThe stenopeic slit shows a difference of 4.50 in the two\\nprincipal meridians bearing this fact in mind, if a 4.50\\ncylinder at axis 1 5 be placed before the right eye, then all\\nmeridians would be made equally hyperopic 2 D. Com-\\nbining 2 sph. with the 4. 50 cylinder at axis 15 in the\\nright eye or at axis 165 in the left, the refraction would be\\ncorrected.\\nOr, if a +4.50 cylinder at axis 105 be placed before the\\nright eye, then all meridians would be made equally my-\\nopic 2 D. Combining a 2 sph. with this +4.50 cylin-\\nder at axis 105 in the right eye or at axis 75 in the left eye,\\nthe refraction would be corrected.\\nFor a further consideration of combination of lenses see\\npage 51.\\nThe rule for ordering cylinders is the same in mixed\\nastigmatism as in other cylindric corrections without\\nchange.\\nSummary. The character of the astigmatism is regu-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0261.jp2"}, "262": {"fulltext": "2 54 REFRACTION AND HOW TO REFRACT.\\nlar, symmetric, and with the rule. The near point returns\\nto the normal for the age. Eyes with such errors do not,\\nas a rule, obtain a visual acuity of for the reason that\\nchanges have taken place in the eye-ground, especially at\\nthe macula.\\nCase VIII. Irregular Astigmatism.\\nApril 2d. Mary Smiles. Age, ten years. Scholar.\\nVI\\nO. D. V. xxx slowly. No p. p. obtained.\\nVI\\nO. S. V. yj^. No p. p. obtained.\\nHistory of poor sight ever since an attack of measles\\nwhen two years of age, at which time was kept in a dark\\nroom for six weeks. Eyes were never strong afterward\\nalways very sensitive to light. Child was sent home from\\nschool with a note from the teacher Mary is near-\\nsighted and should see a doctor.\\n.S. P. Eyelids appear normal. Excessive epiphora.\\nCorneas nebulated, especially O. S., which has a decided\\nleukoma at the pole. Anterior chambers of normal depth.\\nPupils 3 mm., round. Corneal reflex very irregular.\\nOphthalmoscope. No view obtained of the eye -ground\\nthrough the small pupils on account of corneal opacities.\\nHomatropin mydriasis shows O. D. cornea faintly nebu-\\nlated in scattered areas rest of media clear. Nerve small\\nand round. Vessels at axis 3 5 degrees best seen with -J- 2\\nD. O. S., there is a 3 mm. area of opacity at the pole of the\\ncornea no clear view of the eye-ground. Indirect method\\nshows a small nerve and refraction hyperopia\\nR Atropin and dark glasses for refraction.\\nApril 2 2d Retinoscope at 1 meter shows band of light\\nat axis 35, indicating hyperopia. Other meridians very\\nirregular. 0. S., nothing definite made out.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0262.jp2"}, "263": {"fulltext": "APPLIED REFRACTION.\\n255\\nPlacido s disc shows irregular, distorted circles.\\nWith Pin-hok Disc.\u00e2\u0080\u0094O. D. V. O. S. V.\\nWith Stenopeic Slit. Axis 45 degrees before O. D. and\\nwith +2.25 S., V. O. S., can not improve\\nvision with any glass.\\nAt Trial-case. O. D., -f-2.00 cyl. axis 145\\nO. S., no glass accepted.\\nApril 23d At trial-case O. D., -f- 1.75 cyl. axis 35\\nFor Mary Smiles.\\nR O. D., 0.25 sph. 3 +1.75 cyl. axis 35 degrees.\\nO. S., plane glass.\\nSig. Constant use.\\nConsiderations. This case shows the advantage of the\\nstenopeic slit and the use of the pin-hole disc. The near\\npoint could not be obtained on account of the poor visual\\nqualities and the child s inability to appreciate what was\\nwanted.\\nCase IX. Tonic Cramp or Spasm of the Accommo-\\ndation.\\nMrs. L. Age, twenty-four years.\\nVI\\nO. D. V. xxv p. p. 9 cm. Add., 24 degrees. Abd., 6\\ndegrees. Esophoria, 4 degrees.\\nVI\\nO. S. V. -xxy p. p. 9 cm. No vertical deviation.\\nHistory of having had glasses changed on three different\\noccasions during the past year. Drops were used each\\ntime, and the three prescriptions were all different. Glasses\\nwere always satisfactory for the first week, but after this\\ntime she was always able to see better at a distance with-\\nout them. Has pains in her eyes and all over the head\\nwhenever she attempts to use the eyes with or without any\\nglasses. Headaches nearly set her wild if she tries to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0263.jp2"}, "264": {"fulltext": "256 REFRACTION AND HOW TO REFRACT.\\nconcentrate her vision on a distant or near object. Has not\\nbeen able to read or write or sew for the past two years.\\nHas been under the care of the gynecologist and neurologist,\\nand they each pronounce her physical condition as normal.\\nThe neurologist suggests a diagnosis of hysteria.\\nPatient sleeps well and has a good appetite, but will suffer\\nfrom nausea and vomiting if she uses her eyes for any length\\nof time. Patient has been married five years. Has one living\\nchild. No miscarriages. Is apparently in the very best\\nof health, and is provoked with her apparent good health\\nas not being consistent with her suffering, and hence she\\ndoes not receive any sympathy fpom her family or her\\nfriends.\\nS. P. No external manifestations of any ocular irregu-\\nlarity.\\nManifest Refraction.\\nVI\\nO. D., 0.50 S. O -)-i.oo cyl. axis 90 degrees -yj-.\\nO. S., the same as O. D.\\nOphthalmoscope. O. D. and O. S., media clear. Discs\\nvertically oval, eye -grounds woolly. Accommodation\\nvery active. Shot silk retina. Refraction is compound\\nhyperopic astigmatism.\\nCobalt-blue glass shows a red center and broad blue halo.\\n(Patient is certainly accommodating.)\\nR Atropin and dark glasses for refraction.\\nStatic Refraction.\\nVI\\nO. D. +1.50 S. 1 75 cyl. axis 90 degrees -y-\\nO. S. -I-1.50 S. 1 75 cyl. axis 90 degrees V t\\nPatient states that her pains and headaches all disap-\\npeared after using the drops for the third time.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0264.jp2"}, "265": {"fulltext": "APPLIED REFRACTION. 2 57\\nRefraction repeated on three different occasions, and the\\nfollowing prescription given\\nFor Mrs\\nL.\\nR.\\n0.\\nD.,\\ni\\n.25 S.\\no\\n+1\\n\u00e2\u0080\u00a275 cyl.\\naxis\\n90 degrees.\\n0.\\nS.\\ni\\n.25 S.\\no\\n+1\\n\u00e2\u0080\u00a275 cyl\\naxis\\n90 degrees\\nGlasses properly centered, and accurately adjusted.\\nAfter ten days patient returns with the statement that\\nher pains and aches have recurred as before, and that she\\ncan see better at a distance without her glasses. With\\ncorrection, each eye sees and with both eyes can see\\n^^r. Add., 20 degrees, and abd., 8 degrees. No verti-\\ncal deviation. Has 3 of esophoria at 6 meters.\\nR Atropin of a grain to the ounce.\\nSlG. To use one drop in each eye each morning and noon.\\nTo wear a pair of dark glasses with her prescription glasses\\nwhen exposed to any bright light. Not to attempt any\\nnear-work. This treatment was continued, off and on, for\\nsix months. Patient was always free from ocular pain and\\nheadache as long as the atropin was being used, but as\\nsoon as the ciliary muscle commenced to contract, then the\\npains would return with all their former severity. This\\npatient eventually recovered by using her distant correc-\\ntion with a pair of plus 2 spheres as hook-fronts for any\\nnear-work.\\nCase X. Exophoria.\\nMiss. V. B. D. Age, twenty-two years.\\nO. D. V. -^j-. p. p. 0.50 D., type at n cm.\\nVI\\nO. S. V. -yj-. p. p. 0.50 D., type at II cm.\\nAdd. and abd., 12 degrees. Exophoria 4.\\nHistory of seeing double several times a day. Friends\\nand members of her family have told her she was squint-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0265.jp2"}, "266": {"fulltext": "258 REFRACTION AND HOW TO REFRACT.\\ning. Always returns home with a severe occipital head-\\nache after going shopping or to any place of amusement.\\nHas headache when using her eyes, but it soon passes\\naway after resting the eyes.\\n5. P. Eyes markedly out under cover. Irises react\\npromptly to light, accommodation, and convergence.\\nFixation test shows the right eye divergent.\\nOphthalmoscope. O. D. and O. S. No apparent changes,\\nand refraction almost emmetropic some small amount of\\nhyperopia and astigmatism.\\nR Atropin and dark glasses for rest and careful refraction.\\nStatic refraction, after several repetitions, O. D. and O.\\nS., +0.50 S. +0.37 cyl. axis 90 degrees And\\nthis is ordered, less 0.25.\\nWith this correction carefully centered, add. 14 degrees\\nand abd. 12 degrees, with 3 of exophoria at 6 meters and\\n7 degrees of exophoria at 1 3 inches. This patient was given\\nprism exercises for more than two months, and, finally,\\nafter the adduction reached 30 degrees and abduction was\\n10 degrees and 3 degrees of esophoria were obtained, the\\nprism exercises were stopped, and patient told to report\\npromptly if any discomfort arose at any time. To wear\\nher glasses constantly.\\nCase XL Anisometropia.\\nMr. Albert S. Age, twenty-nine years. In general business.\\nVI\\nO. D. V. lx~. p. p. type 0.50 D. 20 cm.\\nVI\\nO. S. V. xxx- p. p. type 0.75 D. 30 cm.\\nAdd., 10 degrees. Abd., 6 degrees. Left Hy., 2 degrees.\\nHistory. Has had three pairs of glasses ordered, with\\ndrops, during the past eighteen months. Has never\\nhad any but the very slightest relief from ocular pains and", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0266.jp2"}, "267": {"fulltext": "APPLIED REFRACTION. 259\\nfrontal headaches, which have been almost constant for the\\npast four years or more. On account of the ocular dis-\\ncomfort and headaches, the patient has given up all at-\\ntempts to read for more than fifteen minutes at a time.\\nPatient states that if he uses his. eyes for more than this\\nlength of time they become bloodshot and very tender\\nto the touch. General health of patient is excellent has\\na good appetite and sleeps well. Does not use tobacco or\\nliquor of any kind.\\n5. P. Face symmetric. Nose very prominent. Inter-\\npupillary distance, 62 mm.\\nOplitlialmoscope. O. D., nerve-head over capillary. Not\\nswollen. Accommodation veiy active. Eye-ground fluffy.\\nRefraction is that of compound hyperopia. O. S., same\\ngeneral conditions, but the nerve is vertically oval and the\\nrefraction is that of hyperopic astigmatism.\\nR Atropin and dark glasses for refraction.\\nStatic Refraction.\\nO. D., -f- 2.00 S. C+1.00 cyl. axis 75 degrees\\nO. S., -f 0.25 S. O -f 3.00 cyl. axis 105 degrees\\nR. O. D., -j-1.75 S. O -fi.oo cyl. axis 75 degrees O ^A base U P-\\nO. S., -(-3.00 cyl. axis 105 degrees O base down.\\nSlG. For constant use.\\nThis patient was not made comfortable until he was given\\nfive-grain doses of the bromid of potash three times a day\\nfor four weeks. Is now able to use his eyes without the\\nleast discomfort.\\nVI\\n2A\\nVI\\n[left\\nXL,,,\\nf hyper-\\nVI\\nphoria.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0267.jp2"}, "268": {"fulltext": "CHAPTER XI.\\nPRESBYOPIA.\u00e2\u0080\u0094 APHAKIA.\u00e2\u0080\u0094 ANISOMETROPIA.\\n\u00e2\u0080\u0094SPECTACLES.\\nPresbyopia. The word presbyopia (from the Greek,\\nirpiffftut:, old (p, eye literally means old sight, and\\npatients at the age of forty-five or more years are univer-\\nsally recognized as presbyopes, and the condition of their\\neyes as presbyopic. There is no exact age limit as to when\\npresbyopia shall begin, the advent of presbyopia being con-\\ntrolled by the character of the ametropia and physical con-\\ndition of the eyes themselves. Presbyopia may be described\\nin several different ways, according to the cause i. e. y\\n1. Old sight.\\n2. The condition of the eyes in which the punctum proxi-\\nmum has receded to such a distance that near vision (close\\nwork) is impossible without the aid of convex lenses.\\n3. The condition of the eye in which the lens fibers have\\nbecome more or less sclerotic, and, as a consequence, the\\nlens loses some of its inherent quality of becoming more\\nconvex during contraction of the ciliary muscle.\\n4. The condition of the eye in which the power of the\\nciliary muscle has become weakened.\\n5. The condition of the eye in which the power of ac-\\ncommodation is diminished at the same time that the lens\\nfibers become sclerotic.\\n6. The condition of the eye in which two different refrac-\\ntions (not necessarily two pairs of glasses) are required, one\\nfor distance and one for near vision.\\n260", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0268.jp2"}, "269": {"fulltext": "PRESBYOPIA. 26 1\\n7. The condition of the eye in which one pair of glasses\\nwill not answer for distant and also for near vision.\\n8. Presbyopia may be described as the condition in which\\nnature has instilled a slowly acting but permanent cyclo-\\nplegic (the term cycloplegic is used here in a general sense).\\nCauses of Presbyopia. 1. Age. It is a well-estab-\\nlished fact that in childhood the center of the lens begins\\nto harden, becomes sclerotic or sclerosed, to form a nucleus\\nand this process continuing, eventuates in complete sclerosis\\nat sixty or seventy-five years. The term sclerosis must not\\nbe confounded with opacity.\\n2. Disease. Ordinarily, presbyopia, as applied to the\\nlens, should be recognized as a physiologic process, as a\\npenalty for growing old, though it is a condition which\\nmay be hastened by disease. Any disease, therefore, which\\nwill cause the nutrition of the lens to suffer must event-\\nually interfere with its ability to become more convex during\\naccommodation. The most common ailments that tend to\\nthis result are rheumatism, gout, Bright s disease, diabetes,\\nlithiasis, la grippe, etc. Any disease which will weaken the\\nciliary muscle will produce presbyopic symptoms.\\nPresbyopic Near Points. The near point and power of\\naccommodation in a healthy emmetropic eye, or a healthy\\neye made emmetropic by the addition of correcting lenses,\\nis as follows for certain ages\\nPower of\\nAge. Near Point. Accommodation.\\n40 years, 22 cm. 4.50 diopters.\\n45 28\\n5\u00c2\u00b0 40\\n55 55\\n60 100\\n65 i33\\n70 400\\n75 if oc\\n3-5o\\n2.50\\n1.75 or 2.00\\n1. 00\\no.75\\n0.25\\n.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0269.jp2"}, "270": {"fulltext": "262 REFRACTION AND HOW TO REFRACT.\\nOrdinarily, the average adult holds a newspaper or book\\nat about 33 cm. (13 inches) from his eyes when reading\\nand if he is forty years of age and emmetropic, or is made\\nemmetropic with glasses, he would be using 3 D. of his\\nnormal 4.50 of accommodation, which would leave a reserve\\npower of 1.50 D.; and in this condition, other things being\\nequal, he can maintain a reading distance with comfort. In\\nfact, he could, by using all of his 4.50 D. of accommoda-\\ntion, see objects as close as 22 cm., but not for any great\\nlength of time, as the ciliary muscle would soon relax.\\nThis same patient at forty-five or forty-six years of age will\\nhave lost 1.00 or 1.50 D. of his accommodation, and now\\nhas only about 3 or 3.50 left and if he uses all of it at a\\nworking distance of 33 cm., the ciliary muscle soon yields.\\nIn fact, the ciliary muscle can not be held in such a state of\\ntension without causing all sorts of pains and aches and\\nreflex disturbances and the ciliary effort relaxing suddenly,\\nthe near vision blurs, and the work or reading or sewing\\nmust be put at a greater distance to obtain relief, or else\\nthe effort must be abandoned.\\nSymptoms of Presbyopia. The principal symptom is\\nthat which indicates a recession of the punctum proximum\\nthe patient stating that there is an inability to maintain\\nthe former reading, writing, or sewing distance, and that all\\nnear-work must be held at a greater distance than formerly.\\nSymptoms of accommodative strain may be present if the\\npatient endeavors to force the accommodation to its\\nmaximum.\\nDiagnosis. The age of the patient and the history of\\nhaving to hold reading matter at an uncomfortable distance\\nor a history of good distant vision and an inability to retain\\nclear near vision small objects, to be seen, must be held\\nfar away or at arm s length.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0270.jp2"}, "271": {"fulltext": "PRESBYOPIA. 263\\nCorrection of Presbyopia. The presbyopic state repre-\\nsents a class of patients for whom glasses may be pre-\\nscribed by the manifest refraction, although there are\\nexceptional cases in which a quick cycloplegic will be nec-\\nessary when an amount of astigmatism or cylinder axis is\\nuncertain.\\nFor a working, reading, writing, or sewing distance of 33\\ncm. (13 inches), the writer makes it a rule to add to the dis-\\ntance correction at forty- five years of age a -f- 1 sphere at\\nfifty years of age, a -j- 2 sphere at fifty-five years of age,\\na +2.50 sphere and for sixty or more years, a +3 sphere.\\nThe following table for emmetropic eyes shows these addi-\\ntions for the different years, and also the near and far points\\nwith these additions as well as the range of accommo-\\ndation or play between the near and far points. It will\\nbe observed that the range of 78 cm. at forty-five years\\nrapidly diminishes in the succeeding years, until at sixty\\nthere is only a play of about 3 inches, and at seventy the\\nrange is practically gone.\\nYears.\\nAdd.\\nNear Point.\\nFar Point.\\nRange.\\n45\\n4-1. OO\\n22 cm.\\nIOO cm.\\n78 cm\\n5o\\n-J-2.00\\n22\\n50\\n28\\n55\\n+2.50\\n23\\n40\\n17\\n60\\n43.OO\\n25\\n33\\n8\\n65\\n43.OO\\n27\\n33\\n6\\n70\\n4-3.OO\\n30\\n33\\n3\\n75\\n43.OO\\n33\\n33\\nBecause a patient is fifty years of age does not signify\\nthat he will be able to read at 33 cm. with a pair of +2\\nspheres, or because he is sixty years of age that he can use\\nhis eyes at 33 cm. comfortably with a pair of -j-3 spheres\\non the contrary, this rule that the writer has given only\\napplies to cases of emmetropia. It often happens that pres-\\nbyopic patients state that they do not want glasses for dis-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0271.jp2"}, "272": {"fulltext": "264 REFRACTION AND HOW TO REFRACT.\\ntance that they do not need them that all they wish is a\\npair of glasses to use at near- work, reading, etc. When the\\nvision is taken in such cases, it may be found to be or\\napproximating but the young ophthalmologist must\\nnot be thrown off his guard by this record, as it has already\\nbeen stated that a vision of\u00e2\u0080\u0094 does not by any manner\\nof means prove the existence of emmetropia. Let the sur-\\ngeon make it a constant rule in every case of presbyopia to\\nalways carefully estimate the amount of the distance ametropia\\nfirst, no matter how weak or what its form {sphere or cylinder)\\nand to the residt thus obtained, add the plus sphere which will\\nbe required for the working distance or point at which the\\npatient wishes to see clearly.\\nIllustrative Cases. Case I. Accepts +0.50 sph. for\\ndistance. At forty-five years this case would require\\n1. 50 sph. for reading at a distance of 33 cm.; at fifty years,\\n-j-2.50 sph.; at fifty-five years, -f-3 sph.; and at sixty or\\nmore years, +3.50 sph. Only one pair of glasses is neces-\\nsary.\\nCase II. Accepts 2 s P n for distance at forty-five\\nyears these eyes would require +3 sph.; at fifty years they\\nwould require +4.50 sph.; and at sixty or more years they\\nwould require +5 sph. Two pairs of glasses would be\\nindicated in this case.\\nCase III. Accepts 1.00 sph. for distance at forty-\\nfive years this patient could read without any glasses, as\\n1 for distance would be neutralized by the -f- 1 required\\nfor reading. At fifty years, however, the patient would\\nrequire a -f- 1 sphere for near, and at fifty-five a 1.50, and\\nat sixty years a -j- 2 sphere. Case II required two correc-\\ntions, one for distance and one for near and the same may\\nbe said about Case III but in this latter instance there was\\na time at forty-five years when there was no necessity for", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0272.jp2"}, "273": {"fulltext": "PRESBYOPIA. 265\\nglasses for the near-work, as the patient s eyes were in a\\nsuitable condition of refraction to read without them.\\nCase IV. Accepts 3 sph. for distance. At forty-five\\nyears would require 2 sph. for reading at fifty years\\nwould require 1 sph. for reading and at sixty years\\ncan read without any glasses. Such a patient says he has\\ngotten his second sight.\\nCase V. Accepts 4-0.50 cylinder axis 180 for distance\\nand requires the usual additional spheres for the increasing\\nyears for his reading distance.\\nCase VI. Accepts +1.00 sph. O -f-i.oo cyl. axis 180\\nfor distance and requires the spheric additions as the years\\nincrease. Two pairs of glasses should be prescribed.\\nCase VII. Accepts 1 cyl. axis 90 for distance, and\\nrequires +1 cyl. axis 180 to read with at forty-five years\\nof age at fifty years he requires -f- 1 sph. O 1 cyl.\\naxis 180 and at sixty years requires -f-2 sph. O -f I cyl.\\naxis 180. At forty-five years of age this patient is com-\\nmonly spoken of as having simple myopic astigmatism for\\ndistance (against the rule) and simple hyperopic astigmatism\\nfor near (against the rule also) two pairs of glasses are in-\\ndicated throughout life.\\nCase VIII. Accepts 1.00 sph. O 1.50 cyl. axis\\n1 80 for distance, and at forty-five years will need 1.50 cyl.\\naxis 180 for reading at fifty years will require 1. 00 sph.\\nO 1.50 cyl., axis 180 degrees; at sixty years, +0.50\\nsph. O 1.50 cyl. axis 90 degrees.\\nTwo pairs of glasses should be used throughout life.\\nAt forty-five years this patient has a compound myopic\\ncorrection for distance and simple myopic astigmatism for\\nnear at fifty years the correction for near is that of crossed\\ncylinders (mixed astigmatism) and at sixty years the near\\ncorrection is that for compound hyperopic astigmatism.\\n2 3", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0273.jp2"}, "274": {"fulltext": "266 REFRACTION AND HOW TO REFRACT.\\nCase IX. Accepts i.oo sph. O 2 cyl. axis 90 for dis-\\ntance (mixed astigmatism) at forty-five years, -f- 2 cyl. axis\\n90 is required for reading; at fifty years, -f-1.00 sph. O\\n2.00 cyl. axis 90. Two pairs of glasses are required. At\\nforty-five years the distance correction is for mixed astig-\\nmatism and the reading correction is for simple hyperopic\\nastigmatism.\\nCase X. Accepts 2.00 cyl. axis 180 for distance\\nat forty-five years requires a mixed astigmatism correction\\nfor near at fifty years, a simple hyperopic correction\\nand a compound hyperopic correction at sixty years.\\nIn the above illustrative cases the working distance has\\nbeen calculated at 33 cm., or 13 inches; but as some\\npatients use their eyes at a greater or less distance than\\nthis, the additional convex lenses must be calculated accord-\\ningly. For instance, the weaver at fifty-five years of\\nage who requires -\\\\-2 spheres for distance could not see to\\nweave at 50 cm. if +2.50 spheres were added to his dis-\\ntance correction, all he needs is +3 for his working dis-\\ntance. Or the diamond cutter who wishes glasses to see\\nhis work at 8 inches, if he accepted 1.00 sph. for distance,\\nhe would require 2 sph. at forty-five years of age.\\nIn conclusion, there are three facts in the refraction of\\npresbyopic patients that should receive attention\\n1. Many accept a weak plus cylinder 0.50 at axis\\n180) against the rule. This is presumptive evidence that\\nthe astigmatism is acquired, is lenticular, and is due to the\\nsclerotic changes previously mentioned. The only positive\\nway to prove this fact is by the retinoscope, and by the ab-\\nsence of corneal astigmatism with the ophthalmometer.\\nIf the case has been previously refracted by the same sur-\\ngeon, his record will also confirm this extremely interesting\\noccurrence. According to able authorities, hyperopic eyes", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0274.jp2"}, "275": {"fulltext": "APHAKIA. 267\\nbecome more hyperopic after the age of seventy years,\\nand emmetropic eyes may become hyperopic, and myopic\\neyes less myopic, from the same sclerotic or shrinking pro-\\ncess which takes place in all the ocular tissues as a result\\nof senility. The method of correction by glasses, however,\\nis just the same, and that is to correct the distant vision\\nfirst and then add the near correction.\\n2. An attack of glaucoma may precipitate presbyopic\\nsymptoms, so that when a presbyopic patient asks for fre-\\nquent changes in his corrections, this complication should\\nbe borne in mind.\\n3. The swelling of the lens which occasionally precedes\\nthe formation of some forms of cataract should be remem-\\nbered when the patient develops symptoms of myopia i. e.,\\na reduction in the strength of convex glasses.\\nAphakia (a, priv. pax6 lentil literally means an\\neye without a lens. (See Fig. 161.) An eye which has\\nhad its lens dislocated\\nhas been erroneously\\nspoken of as aphakic.\\nThe absence of the lens\\nmeans a total absence\\nof all accommodation,\\nno matter what the age FlG\\nof the patient may be.\\nCauses. Aphakia may be congenital, but in most cases\\nis the result of removing the lens by operation.\\nDiagnosis. Aphakia may be diagnosed by inspection\\ni. e., corneal scar, depth of anterior chamber, tremulous\\niris, coloboma of the iris, opaque capsule whole or in part,\\nerect corneal image, with absence of lenticular images, and\\nby the patient s history.\\nThe ametropia of an aphakic eye depends in great part", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0275.jp2"}, "276": {"fulltext": "268 REFRACTION AND HOW TO REFRACT.\\nupon the previous refractive condition of the eye, and also\\nupon the kind of operation that was performed for the re-\\nmoval of the lens. It has been calculated that an eye, to\\nbe emmetropic after the removal of its lens, would have to\\nbe myopic at least twelve diopters. If this is always true,\\nthen the correcting lens which is selected by an aphakic eye\\nis a guide to its former ametropia. An eye which selects a\\nweak plus sphere would, therefore, have been myopic before\\nthe operation and if about a -f 12 S., its previous refrac-\\ntion approximated emmetropia if a plus sphere stronger\\nthan 1 2, then the previous refraction was very likely hyper-\\nopia.\\nAn eye which has had its lens removed by absorption\\n(needling) is not likely to be astigmatic whereas, when\\nthe lens has been removed by extraction, astigmatism\\nagainst the rule of one or more diopters almost invariably\\nresults, and the axis of the correcting cylinder generally\\ncoincides with the points of puncture and counterpuncture\\nin the cornea. If a patient had 2 or 3 D. of myopic\\nastigmatism with the rule, this would be neutralized by the\\ncorneal section.\\nCorrection of Aphakia. As in presbyopia, two correc-\\ntions are necessary one for distance and one for near.\\nAstigmatism must always be looked for and carefully cor-\\nrected, especially if the lens has been removed by extrac-\\ntion.\\nCase I.\\nVI\\nO. D., -f8.oo sph. 3 +3-\u00c2\u00b0\u00c2\u00b0 c yl- ax i s IO degrees. V. -^r-\\nO. D., -j-n .oo sph. 3 H-3-\u00c2\u00b0\u00c2\u00b0 c yl- ax i s IO degrees reading at 33 cm.\\nThis patient was presumably myopic before operation.\\nAnisometropia (aWoc, unequal fiirpov, a measure\\nd p, the eye literally means that the ametropia of", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0276.jp2"}, "277": {"fulltext": "ANISOMETROPIA. 269\\nthe two eyes is not exactly the same. This condition\\nmay be slight or one of the most extreme conditions imagin-\\nable. One eye may be hyperopic 4-0.25 D. and the\\nother \u00e2\u0080\u00940.50 D. or one eye may be myopic and the other\\nhyperopic or one eye may be astigmatic and the other\\nnot have any astigmatism or one eye may be aphakic with\\nmany diopters of hyperopia and the fellow-eye be myopic.\\nFor purposes of classification only, the writer would not\\nclass anisometropia as the condition in which the strength of\\nthe glass is different in the two eyes, but in which the character\\nof the refraction is different. For instance, if both eyes have\\ncompound hyperopic astigmatism, they are not considered\\nas anisometropic, even if the sphere and cylinder are of\\ndifferent strength in the two eves. Bearing this distinction\\nin mind, the percentages already given for myopia, hyper-\\nopia, the different astigmatisms, etc., have been calculated\\naccordingly, that for anisometropia being about thirteen per\\ncent.\\nCauses. Usually the condition is congenital, or it may\\nbe acquired.\\nDifficulties. Two difficulties are encountered when\\nordering glasses for cases of anisometropia (1) The lens for\\none eye maybe concave and that for the other may be con-\\nvex, or both eyes may require a convex or both may re-\\nquire a concave lens, but one very much stronger than the\\nother under these circumstances, when the eyes are\\nrotated there will be a prismatic result of different amount\\nin each eye, and this may mean diplopia, or at least an\\nexertion on the part of the extraocular muscles to prevent\\ndiplopia which will cause dizziness, nausea, headache, etc.\\n(2) With lenses as just mentioned, the size of the two retinal\\nimages will not be exactly the same, and this will mean an\\ninterference with clear binocular vision.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0277.jp2"}, "278": {"fulltext": "27O REFRACTION AND HOW TO REFRACT.\\nFor purposes of study, the writer would divide cases\\nof anisometropia into four different classes.\\nClass I. This class embraces those cases in which the\\ndifference in the ametropia between the two eyes is very\\nslight or does not exceed two diopters. In fact, there are\\nvery few pairs of eyes that are not slightly anisometropic\\nsuch eyes usually receive their exact corrections with com-\\nfort, regardless of the condition.\\nClass II. Cases that come under this head also accept\\ntheir exact correction for each eye, but do not attempt\\nbinocular single vision, and may never suffer the least in-\\nconvenience these cases are extremely rare. They do not\\ncomplain of diplopia, as they have learned to ignore the\\nfalse image. Cases of alternating squint, one eye myopic\\nand the other eye hyperopic, may be included in this class.\\nClass III. This is a class which will accept the exact\\ncorrection before one eye only, and the eye which has the\\ngreatest amount of ametropia will refuse almost any lens\\nexcept the very weakest. The eye that has the most ame-\\ntropia is often quite amblyopic.\\nClass IV. This class includes young children especi-\\nally cases of squint. In children the correction as found\\nby the static refraction is usually accepted.\\nThe Prescribing of Glasses in Cases of Anisome-\\ntropia. Excluding Class I, there is no fixed rule to follow\\nwhen ordering glasses in decided cases of anisometropia,\\nand, in fact, such eyes are a constant study to the most\\nable ophthalmologist. The younger the patient, however,\\nthe more likelihood of a favorable result from the careful\\nselection of a glass for each eye but when the patient is an\\nadult, it becomes a very serious question as to what glass\\nto prescribe that will give satisfaction. As good results\\nare to be expected in children, they should receive the", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0278.jp2"}, "279": {"fulltext": "ANISOMETROPIA. 2J\\nmost careful retinoscopic refraction. The child comes under\\nobservation on account of a squint, and an operation for the\\ndeformity is often demanded but the operation must be\\nrefused until the anisometropia has been carefully treated.\\nGlasses having been prescribed, the squinting eye is put to\\nwork to develop its seeing qualities, which have been per-\\nmitted to lie dormant for want of a proper glass. To do\\nthis, the good eye is shielded or blinded with a hand-\\nkerchief tied over it, or a blinder (see Fig. 1 60) placed over\\nits correcting lens, for an hour or two each day, and in this\\nway an attempt is made to bring the vision in the squinting\\neye up to that of its fellow.\\nOr another way to develop the vision in the squinting\\neye is to use a cycloplegic in the good eye, so that the\\nsquinting eye must do most of the work. This is rather\\ntrying to the little patient, and often means the additional\\nuse of dark glasses. As a rule, the good eye has the\\nleast amount of ametropia, but occasionally the reverse con-\\ndition may exist.\\nIn a case like the following, the little girl, five years of\\nage, was brought on account of convergent squint in O. S.,\\nwhich developed or commenced to appear when ten months\\nof age, and the parents attributed it to the habit of sucking\\nher thumb at the time of being weaned. Refraction, with\\natropin as the cycloplegic, and obtained with the retino-\\nscope, showed O. D., -|-2.oo sph.; O. S., 4.00 sph. O\\n4-I.OO cyl. axis 75 degrees.\\nThis child developed the squint on account of the\\nmonocular astigmatism and because it could not accom-\\nmodate sufficiently with the left eye. To avoid diplopia\\nat the same time that the eyes were converging, the\\nleft eye naturally turned inward. With correcting glasses,\\nand practising as above directed, the squint entirely", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0279.jp2"}, "280": {"fulltext": "2/2 REFRACTION AND HOW TO REFRACT.\\ndisappeared, and vision one year later was in each\\neye with the correcting glasses. If the glasses are laid\\naside for any length of time, the squint returns. This\\nchild must wear the glasses or have squint.\\nTo make sure that no injustice is done to an apparently\\namblyopic eye in an adult (Class III, p. 270) where ambly-\\nopia exanopsia has existed for many years and nothing has\\nbeen done to improve its correction, the writer makes it a\\nrule to prescribe the exact correction for each eye, and at the\\ntime of ordering the glasses explains to the patient what\\nthe purpose and desire is, and that if there is any great\\namount of discomfort in any way, he must return and have\\nany necessary change made in the glass. These patients\\nshould be kept under observation and the amblyopic eye\\ngiven some sort of a correction and improved as much as\\npossible; the purpose being not to allow the eye to\\ndegenerate or grow more amblyopic, for if any accident\\nshould befall the good eye, then the amblyopic eye will\\noften be a friend indeed.\\nGlasses for Presbyopes and Cases of Aphakia. Unless\\nthe distant vision is improved or asthenopic symptoms are\\nrelieved by glasses, it will be sufficient to prescribe the\\nnear correction only. When a distant and near correc-\\ntion are required, they may be prescribed as two pairs of\\nglasses in separate frames, or two pairs in one frame, known\\nas bifocals. Bifocals, or what is equivalent to bifocals, are\\nmade in different ways.\\n1. Franklin* or Split Bifocals (Figs. 162 and 163).\\nThis form of bifocals consists of an upper and a lower lens,\\neach with its individual center the upper lens is for dis-\\ntance and the lower for near vision. Such lenses must have\\nthe frame all around the edges, so as to hold them in posi-\\nHistory of Spectacles, L. Webster Fox, Med. and Surg. Reporter,\\n1890, vol. lxii, 513-519.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0280.jp2"}, "281": {"fulltext": "BIFOCALS.\\n273\\ntion. Bifocals of this kind are not in common use. The\\nfield of distant vision is limited by the unnecessarily large\\nnear correction, and where the two lenses come together,\\nFig. 162.\\nFig. 163.\\nthere is apt to develop chromatic aberration and a decided\\nprismatic effect when the vision is directed through this\\nspace.\\nR. O. D., +2.00 sph.\\nO. S., +2.00 sph.\\nSlG. For distance.\\nR. O. D., +4.00 sph.\\nO. S., +4.00 sph.\\nSlG. For near.\\nDirections to Optician. Make into Franklin or split bifocals.\\n2. Morck s Patent or Perfection y Bifocals (Fig.\\n164). These are a modification of the Franklin or split\\nbifocals, and in place of having\\nlenses united in a horizontal line,\\nthe near and distant lenses are\\nfitted together with correspond-\\ning crescent edges. This form\\nof bifocal gives a larger field for\\nthe distance correction, and, like\\nthe Franklin, is much better\\nfor those who work in a damp\\natmosphere and can not wear the cement bifocal. It is,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0281.jp2"}, "282": {"fulltext": "2;4\\nREFRACTION AND HOW TO REFRACT.\\nhowever, more expensive than the cement form but, like\\nthe Franklin, it often looks clumsy or heavy on account\\nof the frame. Perfection or Morck bifocal must be\\nsignified in writing the prescription.\\n3. Cement Bifocals (see Figs. 165 and 166*). This is\\nthe most common form of bifocal and the least expensive\\nin its original cost, as also when making changes in the\\nnear correction. This bifocal is made by cementing a seg-\\nFig. 168\\nFig. 169.\\nment of a small periscopic sphere on to the lower part of\\nthe distance correction. This periscopic sphere or disc or\\nsegment, as it is called, has a prismatic quality (see Fig.\\n166) suitable to the exigencies of the individual lens to\\nwhich it is cemented. The segment may be of any shape\\ndesired. Those in common use are shown in figures 167,\\n168, and 169. It is cemented to the distance correction\\nDescribed by Dr. Geo. M. Gould,\\n1888.\\nMed. and Surg. Reporter, Nov. 3,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0282.jp2"}, "283": {"fulltext": "BIFOCALS.\\n275\\nwith Canada balsam. While this is the usual method of\\nmaking a cement bifocal, yet it may be made by cementing\\nFig. 170.\\nFig\\na concave segment to the upper part of the near correction.\\n(Figs. 170 and 171.) This form is not in common use.\\nR. O. D.,-f 2 S.\\nO. S.. +2S.\\nCement on the lower part of the above O. D. and O. S., -|-2.oo S.\\nSlG. Make frameless bifocals.\\nOr,\\nR. O. D.,+ 4 S.\\nO. S., +4S.\\nCement on the upper part of O. D. and O. S., 2.00 S.\\nSlG. Make frameless bifocals.\\n4. Achromatic Bifocals (Figs. 172 and 173*). This\\nFig. i}2. Fig. 173.\\nform of bifocal is used principally in cases of aphakia where\\nthe plus sphere is quite thick and correspondingly heavy. It\\nBorsch patent.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0283.jp2"}, "284": {"fulltext": "276 REFRACTION AND HOW TO REFRACT.\\nis made in one of two ways (1) By grinding out a portion\\nof the lower part of the distance correction (in crown glass)\\nand cementing into the concavity a biconvex segment\\nof flint glass. This form of bifocal is a combination of\\nthe perfection and lenticular. (2) In place of grinding\\nthe concavity in one lens, as just described, this achromatic\\nbifocal is also made by taking two planoconvex spheres\\nand grinding out a concavity in each, and then inserting a\\nconvex sphere of flint glass, as shown in figure 173 these\\nthree lenses are then cemented together, and when com-\\npleted, look like the cement bifocal, as shown in figure 169.\\nIt is a matter for very careful calculation as to just how\\nstrong to make the flint glass segment, so that the result\\nmay be just exactly right. The merits of this bifocal are\\nlightness and the absence of chromatic aberration. These\\nlenses are very expensive.\\n5. Solid or Ground Bifocals (Figs. 174 and 175).\\nLenses of this character are made in one piece. They\\nFig. 174. Fig. 175.\\nlook neat, but are not always comfortable, on account of\\nthe resulting prismatic effect, which is especially apt to\\noccur when the lens is convex, though this may not be\\nso troublesome a feature when the lens is moderately con-\\ncave.\\n6. Patients who have a very weak distance correction,", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0284.jp2"}, "285": {"fulltext": "BIFOCALS.\\n277\\nand could do without it, sometimes accept it for the con-\\nvenience of wearing bifocals they do not wish to be an-\\nnoyed by taking off or putting on a near correction, prefer-\\nring to have the glasses where they can find them business\\nmen especially. Other patients prefer to do without a\\nFig. 176.\\nFig. 177.\\nFig. 179.\\ndistance correction, and will often use a near correc-\\ntion that has one-third or nearly one-half of its upper\\npart cut away, so that they can look over the near correc-\\ntion when they wish to see at a distance. (See Figs. 176,\\n177, 178, 179, and 180.) Myopes who do not need a\\nnear correction will wear their\\ndistance correction with its lower\\nportion cut away, so that when\\nthey wish to see near at hand,\\nthey can look under the distance\\ncorrection, Fia l8a\\n7. Patients who require a dis-\\ntance correction, and can not get accustomed to cement", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0285.jp2"}, "286": {"fulltext": "278\\nREFRACTION AND HOW TO REFRACT.\\nsegments, and at the same time do not wish to change the\\ndistance correction, but prefer to keep it on all the time,\\ncan put on their addition for near vision in the form of\\nhook or grab fronts of the same size as the distance\\nlenses or reduced one-half in the vertical diameter. This\\nis not always a good combination, as in every instance the\\nlenses do not lie in contact with each other.\\n8. Lorgnettes may be used as a distance correction or as\\na substitute for hook fronts. Some myopic women who\\nwear their near corrections constantly often carry lor-\\ngnettes, which they hold up in front of the near correction\\nto improve distant vision for a few minutes, or, wearing the\\ndistance correction, can use a plus lens in the lorgnettes for\\nnear vision.\\n9. Cases of monocular aphakia where the vision in the\\nfellow-eye is very defective can wear reversible frames, one\\nlens for distance and the other for near, that is to say, a\\nframe which has a free joint at the temples, and in this way\\nthey avoid bifocals, and can change the distance for the\\nnear correction by turning\\nthe temple-pieces.\\nIn some cases of apha-\\nkia where the lens is very\\npowerful, a bifocal segment\\ncan sometimes be dis-\\npensed with, if the patient\\nhas a long nose, by slid-\\ning the lens down from\\nthe eye and then holding the reading matter at the conju-\\ngate focus. A toric lens (Fig. 181) is very acceptable in\\noccasional instances, as it reduces somewhat the weight and\\nthickness of the lens, and also enlarges the field of vision.\\nA toric (torcine or toriqiic twisted lens is one which\\nCopyright, 1886, by Chas. F. Prentice.\\nFig. 181.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0286.jp2"}, "287": {"fulltext": "BIFOCALS. 279\\nhas, combined in one surface, the optic effects of a sphero-\\ncylindric lens, or two cylinders of different strength at right\\nangles to each other. Unfortunately, this kind of a lens is\\nquite expensive.\\nGeneral Considerations. Before prescribing any pair\\nof glasses, the patient should have the opportunity to wear\\nthe correction in the office for a short time, that he may\\nstudy its effect; this is especially necessary (1) when the\\nglasses are strong ones (2) when there is monocular as-\\ntigmatism (3) when one lens is much stronger than the\\nother (anisometropia) (4) when the astigmatism is asym-\\nmetric or (5) when there is a strabismus, etc. The patient\\nloses confidence (and the surgeon is not made happy) when\\nthe patient returns with his glasses in his hands and states\\nthat he can not wear them that they make him dizzy or\\ntipsy that the glasses make the pavement, houses, trees,\\npeople, pictures on the wall, chairs, tables, etc., all appear\\nas if they were going to fall to one side. The surgeon\\nshould have anticipated all this, and assured the patient\\nbeforehand that, after a little perseverance and practice, this\\ndistortion (parallax) will disappear and if not, then a\\nchange will have to be made in the glasses. Very often\\nthe whole difficulty is due to a want of proper centering of\\nthe lenses, presuming, of course, that the glasses ordered\\nare perfectly correct.\\nPatients who require weak lenses spherocylinders or\\ncylinders alone may at some time be informed that the\\ncorrection is but window-glass, and thus the surgeon may\\nbe put in disgrace as having prescribed for mercenary\\nreasons, when in truth the glasses have already cured an\\nold blepharitis or asthenopia. In ordering weak correc-\\ntions, therefore, the character and purpose of the glasses\\nshould be imparted to the patient.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0287.jp2"}, "288": {"fulltext": "280 REFRACTION AND HOW TO REFRACT.\\nIt is interesting to notice that strong glasses are usually\\nordered to improve the vision, and not always for the relief\\nof asthenopia, whereas weak corrections are prescribed for\\nthe relief of headaches, etc., without any decided improve-\\nment in the vision which the patient can appreciate when\\nlooking at a distance, and many such patients will say they\\ncan see just as well without their glasses. When strong\\nplus spheres are prescribed for a child, it will do no harm\\nto inform the parents of the character of the glasses, so\\nthat when a presbyope tries the child s glasses, the sur-\\ngeon may not be accused of ruining the child s eyes by\\nhaving ordered a pair of glasses strong enough for a grand-\\nmother to read with, and the child hurried off to a rival\\nconfrere to have the outrage rectified.\\nA patient who has fought against the inevitable, using\\nheadache powders, liver pills, etc., in the vain hope of not\\nhaving to put on glasses, may still object to their use for\\nvarious reasons. It may be that glasses will not add to\\nthe personal appearance, or the parents may dislike the\\nidea, fearing that the oculist puts glasses on every\\npatient, or that the eyes will never be the same again,\\nor that the habit of wearing glasses, once established, can\\nnever be stopped. These and many other statements will\\nserve to enliven the daily routine of ophthalmic practice.\\nThese objections having been met from the point of view\\nof the patient s individual welfare and future good of his\\neyes/ the next question that arises is what form of glasses\\nshall be prescribed.\\nSpectacles. The child is certainly a candidate for spec-\\ntacles. The frames must be very durable, and preferably\\nof 14-carat gold. Spectacle frames keep the lenses in posi-\\ntion, and the lenses are then less liable to be broken than\\nin the form of eye-glasses, and for most occupations are to", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0288.jp2"}, "289": {"fulltext": "BIFOCALS. 28l\\nbe preferred. Occasionally, the shape of the nose will pre-\\nclude the use of anything else but spectacles. When one\\nlens is very heavy or both have considerable weight, or\\nwhen one or both lenses are cylindric, with axes inclined,\\nspectacles are certainly indicated.\\nEye-glasses, also called pinc-nez, are for the adult,\\nand may be prescribed when the lenses are not too heavy,\\nor the cylinders too strong or their axes inclined. Eye-\\nglasses are easily bent, and lose their exact positions before\\nthe eyes. For the young society girl nothing but the most\\ndelicately made eye-glasses will, as a rule, be accepted.\\nBifocals. These should not, as a rule, be prescribed if\\nthe lenses are very strong or the correction a complicated\\none, or the patient advanced in years and has never at-\\ntempted them before, or if the patient is very portly or\\nuncertain in his gait, or the vision is not brought close to\\nthe normal. Two separate pairs of glasses are to be recom-\\nmended under these circumstances. When ordering any\\npair of bifocals, the patient should be cautioned and in-\\nstructed that when looking downward, going up or down\\nstairs, getting into or out of a conveyance, he is to look to\\none side or over the segment of the bifocal and not\\nthrough it, otherwise he will be liable to make a false step\\nor misjudge the distance, which might mean serious bodily\\ninjury, for which the surgeon does not wish to hold himself\\nresponsible.\\nGlasses for constant use should be placed perpendicularly\\nor at an axis of about 5 degrees to the plane of the face,\\nwith the optic centers corresponding to the pupillary cen-\\nters when the eyes are directed to a distance. If the lenses\\nare unusually strong and to be used principally at near-\\nwork, then it may be necessary to consider the advisability\\nof having two pairs of glasses, one for distance and one\\n24", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0289.jp2"}, "290": {"fulltext": "252 REFRACTION AND HOW TO REFRACT.\\nfor near, each with the centers to answer for the object in\\nview. If only one pair of glasses has been ordered, and\\nthey happen to be very strong, then a pair of prisms in\\nhook fronts may have to be used at the near-work, so as to\\ncounteract the prismatic effect of looking through the dis-\\ntance glasses during convergence. Glasses for near-work\\nonly should be put into a frame made especially for the\\npurpose, so that the lenses may have an inclination in\\nkeeping with the downward turn of the eyes, and thus be\\nperpendicular to the axis of the eyes, and the lenses should\\nbe decentered inward to equal the convergence. The one\\nserious objection to bifocals in certain instances is that the\\nglasses can not be made with the inclination suitable for\\nboth distance and near vision, and very often there must be\\na compromise between the two.\\nThe surgeon should make it a point to carefully inspect\\nevery pair of glasses which he orders, as his painstaking\\nefforts and best endeavors may be completely frustrated by\\npoorly fitting lenses.\\n1. The lenses should neutralize. (See p. 56.)\\n2. The optic centers should be at the points indicated.\\n3. The cylinder axes must be exact.\\n4. The lenses must be perpendicular or inclined to the\\nfront of the eye, as necessary.\\n5. The distance of the lenses from the eyes should\\nalways be sufficient to clear the lashes and if these are\\nvery long, they may have to be trimmed.\\n6. The most convex or the least concave surface of the\\nlens should be placed away from the eyes. Or the most\\nconcave surface toward the eye.\\n7. The lenses should be of the correct size for the indi-\\nvidual face. These and many other points for the average\\ncase must receive the careful consideration of the surgeon.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0290.jp2"}, "291": {"fulltext": "TRIFOCALS. 283\\nTinted or Colored Glasses. Except for the relief of\\nphotophobia following cataract extraction, mydriasis, or\\ninflammatory diseases, the surgeon does not order colored\\nglasses. Colored lenses are to be deprecated except in the\\ncases just mentioned, as they only increase the tendency to\\nphotophobia instead of correcting it.\\nPerimetric Lenses. These are made to conform in out-\\nline to the normal field of vision as recorded by the per-\\nimeter, hence the name.*\\nThe usefulness of the perimetric lens is limited to those\\ncases in which the correction contains a plus cylinder and\\nthe lens is of moderate strength. It is not a lens that can\\nbe prescribed in myopia or aphakia. The purpose of the\\nperimetric lens is to give a normal field and have the edge of\\nthe lens sufficiently removed that the patient may not be\\ndisturbed by seeing it. It certainly enlarges the field of\\nvision, and in this way is a great advantage in certain occu-\\npations, playing the piano, etc. Figure 188 or 189 may\\nanswer the same purpose if properly centered.\\nTrifocals. Occasionally, a patient is not content with\\nbifocals, but will demand a focal point somewhere between\\ninfinity and his working distance this can only be pro-\\nduced by cementing two segments of different sizes and\\nstrength on the distance correction. Bookkeepers who have\\nto work at large and lengthy ledgers find great comfort in\\nthis combination, though to be of special service the lenses\\nmust be made large.\\nDecentering of Lenses. Instead of writing a prescrip-\\ntion for a lens and prism, the prismatic effect of the lens\\nmay be obtained by decentering the lens. The rule is\\nThe writer described this form of lens before the Section in Ophthalmology\\nof the College of Physicians of Philadelphia, in March, 1897.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0291.jp2"}, "292": {"fulltext": "284 REFRACTION AND HOW TO REFRACT.\\nthat for every centimeter of decentering there will result\\njust as many prism-diopters as there are diopters in the\\nmeridian of the correcting lens. For example, -f-4 sph. O\\n4 P. D., base out, is the same as +4 sph. decentered 1 cm.\\noutward or -f-4 sph. O 2 P. D., base in, equals -f-4 S.\\ndecentered 5 mm. inward or -j- 2 sph. O -f 2 cyl. axis\\n90 degrees O 2 A, base outward, equals -j- 2 sph. O -f 2\\ncyl. axis 90, decentered 5 mm. outward.\\nWhile it is well for the student to know how to decenter\\nlenses, yet the writer does not recommend such lenses,\\npreferring, when necessary, to order a prismatic combina-\\ntion, and have the optician fill the prescription, starting\\ndirect from the prism.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0292.jp2"}, "293": {"fulltext": "CHAPTER XII.\\nLENSES, SPECTACLES, AND EYE-GLASS\\nFRAMES. HOW TO TAKE MEASURE-\\nMENTS FOR THEM AND HOW THEY\\nSHOULD BE FITTED.\\nThe selection of the size and shape of lenses, the char-\\nacter of the spectacle and eye-glass frames and their adjust-\\nment, is the work of the optician. It occasionally happens,\\nhowever, that the surgeon may not have an optician in his\\ntown, and will, therefore, have to take the necessary meas-\\nurements himself and send them, with his prescription, to\\nan optician in a neighboring city. This chapter is there-\\nfore added for the benefit of such surgeons. It is hardly\\nnecessary to state that the frames should be very carefully\\nadjusted and the lenses centered to the patient s eyes. A\\nlens improperly adjusted may utterly destroy the good\\neffect of the most skilfully selected correction, giving dis-\\ncomfort to the patient and reflecting seriously upon the\\nsurgeon s ability. In fact, it is always well for the surgeon\\nto personally inspect every pair of glasses which he may\\norder.\\nLenses. These are spoken of as eyes, and come in\\nvarious sizes and shapes. They are spoken of as O, double\\nO (00), triple O (000), etc. (See Figs. 187, 188, 189,\\n190, and 191.) Or sizes smaller than O are numbered 1, 2,\\n3, or 4. (See Figs. 182, 183, 184, 185). Different shapes\\nand sizes are lettered A, B, C, D, F, or X. (See Figs. 176,\\n177, 178, 179, 180, 186.) All these lenses are also marked\\n285", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0293.jp2"}, "294": {"fulltext": "286\\nREFRACTION AND HOW TO REFRACT.\\nin millimeters of breadth and length. The lenses for indi-\\nvidual patients are selected according to the purpose for\\nwhich they are intended, and particularly to be in keeping\\nFig. 182.\\nFig. 183.\\nFig. 184.\\nFig. 185.\\nFig. 186.\\nFig. 187.\\nwith the facial measurements. The size or eye O (39 X 30\\nmm.) is the usual size for the average adult, and number\\n2, 3, or 4 is for a child. C, D, or F may be ordered for a", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0294.jp2"}, "295": {"fulltext": "LENSES.\\n287\\npresbyope who does not need a distance glass and who\\ndoes not wish to be taking off the near correction to see at\\nFig. 190.\\nFig. 19\\na distance in other words, such a shaped lens can be\\nlooked over without any difficulty. Or the presbyope who", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0295.jp2"}, "296": {"fulltext": "255 REFRACTION AND HOW TO REFRACT.\\nrequires a 2 for distance and can see to read without\\nany near correction, being about fifty years of age, could\\nhave his minus lenses made in the shape of A, B, C, or D\\ninverted, and, wearing this for distance, would look under\\nit when he wished to see near at hand. As a rule, the\\npatient with a narrow face and short interpupillary distance\\nwill require a small eye, whereas the patient with a\\nbroad face and long interpupillary distance will require a\\nlarge eye.\\nSpectacle Frames (Fig. 196). These consist of a nose-\\npiece (called the bridge) and temples (called sides). These\\nare attached to the lenses eyes by screws passing\\nthrough holes which have been drilled through them, mak-\\ning what is known as the frameless spectacles or a wire is\\nfitted around the lenses, to which the bridge and sides are\\nattached with solder, forming the framed spectacles.\\nEye-glass Frames (Fig. 197). These consist of a\\nspring and nose-pieces the latter are called guards.\\nFramed and frameless eye-glasses have the nose-pieces or\\nguards attached to the lenses as in the spectacles.\\nHow to Take Measurements. There are three points\\nthat require particular attention (1) The center of the\\nlens should correspond with the center of the pupil (2)\\nthe lens must be just far enough from the eyes to avoid the\\nlashes, and if these are very long, they must be trimmed\\n(3) the lens must be at such an angle that the visual axis\\nwill be perpendicular to it.\\nFirst Measurement. The Interpupillary Distance. To\\naccurately measure the distance from the center of one\\npupil to the center of the other is not always an easy thing\\nto do, especially if the pupils are dilated hence, it is good\\npractice to measure this distance from the inner side or edge\\nof one pupil to the outer edge of the other. This measure-", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0296.jp2"}, "297": {"fulltext": "FIRST MEASUREMENT.\\n289\\nment can be made with an ordinary rule divided to six-\\nteenths of an inch or in millimeters, or with a special instru-\\nment for the purpose, called a pupilometer. The patient\\nis told to look directly to the front, at an object across the\\nroom, and the surgeon, in front, with his head. nearly in the\\nline of sight, holds the rule across the patient s face, as\\nclose as the bridge of the nose or eyelashes will permit.\\nWith his thumb-nail as a marker, the surgeon gages the\\ndistance as indicated (see Fig. 192), which illustrates the\\nconditions. In taking this measurement the surgeon should\\nbe at an arm s length from the eyes, for the reason that his\\nFig. 192.\\nown eye forms the apex of a triangle of which the eyes of\\nthe patient form the base, and the measurement is apt to\\nbe two or three or four millimeters short if he gets too\\nclose.\\nIf the glasses are to be worn for distance only, then the\\nmeasurement must be for the full interpupillary distance, as\\nthe patient looks into infinity but if the glasses are for near-\\nwork only, then the distance between the pupils must be\\ncorrespondingly diminished, and the measurement taken\\nas the patient looks at a near point. If the glasses are\\nto be worn for both near and far vision, for constant use,\\n2 5", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0297.jp2"}, "298": {"fulltext": "290\\nREFRACTION AND HOW TO REFRACT.\\nthen the center of the lenses must be placed intermediate\\nbetween the distance and near measurements.\\nSecond Measurement. The Bridge. The regulation\\nspectacle bridge is known as the saddle-bridge, and should\\nconform to the exact shape of the patient s nose. It is in-\\ntended to remain in just one place, and that is at the bridge\\nof the nose (see B in Figs. 193 and 194), the place where\\nthe nose begins to extend outward after passing down from\\nthe forehead. The points B and D, as shown in figure 195,\\nrepresent the widest part or base of the bridge. A and R\\nare the arms, which extend upward or outward and are\\nfastened to the lenses. The length of the arms controls in\\nFig. 193.\\nFig. 194.\\ngreat part the distance of the lenses from the eyes. To\\nraise or lower the position of the lenses in front of the eyes,\\nthe posts or arms alone should be bent the bridge itself\\nsJwuld never be tilted, as its edge will cut into the skin of\\nthe nose this is a most important consideration for the\\npatient s comfort.\\nThe Shape and Size of the Bridge. To take this meas-\\nurement, the surgeon should have a piece of lead-wire or\\nthin, pliable copper-wire the lead-wire is best. This wire\\nis accurately molded to the bridge of the patient s nose,\\nthe arms (A and R) are bent to the proper angle, and then\\nthe ends of the wire are curved or bent outward to show\\nthe plane of the lenses. (See Fig. 195.)", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0298.jp2"}, "299": {"fulltext": "THIRD MEASUREMENT FOURTH MEASUREMENT. 29 1\\nWhen the wire has been bent into place and the eyelashes\\ndo not touch at L and L, it is removed and placed on the\\nunder surface of a piece of paper, when an impression and\\nlead-pencil tracing is made of it. If the measurement is\\nnot taken in this way, then the surgeon, with a pair of\\nmoderately blunt-pointed compasses, measures the breadth\\nof the nose from B to D, and also the height of the bridge\\nfrom F to E. The height of the bridge is spoken of as\\nout or in the former when F extends beyond the\\nplane, and in when F is behind the plane of the lenses.\\n(See Figs. 193 and 194.)\\nAnother good way to take the foregoing measurements\\nis to have several ordinary steel frames of different sizes and\\nFig. 195.\\nshapes, using whichever one of these seems to fit the best,\\nand then making any additional alterations in the measure-\\nments that may be required.\\nThird Measurement. This is the length of the sides or\\ntemples. This measurement is taken from the top of the\\near to the plane of the lens, or a horizontal line extending\\nout from the eyelashes.\\nFourth Measurement. The Size of the Lenses. This\\nwill depend upon the breadth of the face, the amount of\\nspace taken up by the bridge, its arms and attachments, as\\nalso the space occupied by the hinge and attachment of the\\ntemples. Ordinarily, as stated before, the adult will select\\nsize O and the child No. 2.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0299.jp2"}, "300": {"fulltext": "292 REFRACTION AND HOW TO REFRACT.\\nThe following blank is a good guide, as covering all\\nthe necessary measurements as referred to in this descrip-\\ntion for ordinary glasses.\\nSTYLE OF BLANK FOR THE SURGEON TO FOLLOW WHEN\\nORDERING GLASSES FOR HIS PATIENT.\\nPatient s Name,\\nForward to,\\nR\\nO.\\n0.\\nD.\\nS.\\nDistance\\nor\\nNear Frames.\\nties\\nof.\\nSpectacles.\\nInterpupillary distance,\\nHeight of bridge,\\nBase of bridge,\\nShape of bridge (see drawing)\\nBridge, in or out,\\nMeasurements.\\nEye-glasses.\\nInterpupillary distance,\\nLength of guard, W to T,\\nWidth at base, W to D,\\nWidth at top, T to P,\\nLength of arm of guards,\\nLength of temples, Shape of spring (see drawing),\\nSize of eye, Size of eye,\\nAdditional notes,\\nDate,\\nM.D.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0300.jp2"}, "301": {"fulltext": "STYLE OF FRAMES.\\n293\\nStyle of Frames. If the glasses are to be worn con-\\nstantly, they should be perpendicular or inclined about 5\\ndegrees from the perpendicular to the front of the eyes.\\n(See Fig. 198.) They are spoken of as distance frames.\\nFig. k\\nFig. 199.\\nIf the glasses are to be worn only at near-work, then the\\nlenses should be tilted downward this is known as the\\nnear frame. (See Fig. 199.)\\nFitting Eye-glasses. The position of the lenses ap-\\nplies equally well for eye-glasses. The\\nprincipal measurement, therefore, is the\\nnose-pieces or guards and the arms or\\noffsets from the guards. (See Fig. 200.)\\nThe width of the patient s nose where\\nW and D, and also T and P, will press,\\ndepends, of course, upon the length of\\nthe guard itself usually about 14 mm.\\nIt is also necessary to measure the posi-\\ntion of the guards relative to the plane\\nof the lenses that is, whether the arms should be long,\\nmedium, or short, and whether they are out or in", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0301.jp2"}, "302": {"fulltext": "294 REFRACTION AND HOW TO REFRACT.\\nfrom the plane of the lenses. The style of spring is usu-\\nally that shown in figure 200.\\nBifocals. The measurements for bifocals are the same\\nas for the spectacle or eye-glass, except the size and shape\\nof the segment, and this should never extend above the\\nmedian line of the lens, and seldom to it.\\nQuality of Frame. These are made of silver, steel,\\naluminium, or gold the latter are always to be preferred,\\nas more durable in every way. Silver and aluminium bend\\neasily, and steel frames rust and break. Every surgeon\\nwho does his own fitting should possess a small screw-\\ndriver, two pairs of delicate and yet strong pliers (one with\\nround and the other with flat ends), and also a small rule.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0302.jp2"}, "303": {"fulltext": "INDEX.\\nA.\\nAbduction, 175\\nAberration, negative, 171\\npositive, 171\\nAbsorption of light, 1 1\\nAccommodation, 64\\namplitude of, 68, 69, 70\\nat different ages, 69\\nbinocular, 82\\ncramp of, 210, 211\\ndiminution of, 260\\nin hyperopia, 69, 70, 71\\nin myopia, 71, 72\\nin presbyopia, 261\\nmechanism of, 65, 66, 67\\nmuscle of, 65\\nobserver s, 96, 97, 156\\nparalysis of, 208, 209, 210\\nspasm of, 2IO, 211\\nAcuteness of vision, 62, 63\\nin astigmatism, 76, 77\\nin emmetropia, 63, ioi\\nin hyperopia, 109\\nin myopia, 115\\nrecord of, 76, 77, 78\\nAdduction, 175, 176\\nAerial image, 99\\nAge, 216\\nAlbino, 91\\nAlternating strabismus, 189, 190\\nAmblyopia, 115, 155, 193\\nAmetrometer, 146, 147\\nAmetropia, 103, 191\\naxial, 103, 104\\ncurvature, 103, 151\\nAngle alpha, 85\\ncritical, 19\\ngamma, 83, 85\\nof convergence, 82\\nof deviation, 23\\nof five minutes, 63\\nof incidence, 21\\nAngle of refraction, 22\\nof strabismus, 194, 195\\nof view, 60\\nAnisometropia, 258, 259, 260, 268,\\n269, 270\\nclassification of, 270\\ncorrection of, 270, 271, 272\\nAnterior focal point, 59, 60\\nfocus, 59, 60\\nApex of prism, 22\\nAphakia, 155, 267, 268\\ncauses of, 267\\ndiagnosis of, 267\\ntreatment of, 268\\nAqueous humor, 67\\nAsthenopia, 211\\naccommodative, 212, 213, 214\\nmuscular, 178, 212, 213\\nretinal, 212, 213\\ntreatment of, 213\\nAstigmatic charts, 135, 136, 137, 138,\\n139\\nclock-dial, 135, 136, 137, 220\\nlens, 121\\nAstigmatism, 120, 167, 167, 232\\nagainst the rule, 129, 130\\nasymmetric, 128\\ncauses of, 122\\ncompound hyperopic, 125, 126,\\n152, 245, 246, 247\\nmyopic, 126, 152, 248, 249,\\n250\\ncorneal, 121\\ndiagnosis of, 13 1\\nestimation of, 222, 223. (See\\nChapter VI.)\\nheterologous, 126\\nheteronymous, 126\\nhomologous, 126\\nhomonymous, 130\\nirregular, 122, 123, 1 69, 1 70,\\n254, 255\\n295", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0303.jp2"}, "304": {"fulltext": "296\\nINDEX.\\nAstigmatism, lenticular, 122\\nmixed, 126, 127, 152, 169, 250,\\n251, 252, 253\\nphysiologic, 12\\nprincipal meridians in, 120, 167,\\n168, 169\\nregular, 123, 124, 125, 126, 127\\nshape of disc in, 151\\nsimple hyperopic, 124, 125, 152,\\n239, 240, 241\\nmyopic, 125, I5 2 2 43\\nstatistics of, 232\\nsymmetric, 127, 128\\ntests for, 1 31-15 1\\ntreatment of, 222, 223\\nwith the rule, 129, 130\\nAtropin, 201, 202, 203, 226\\nAxiom, 155\\nAxis of astigmatism, 128, 129\\nof cylinder, 128, 129, 222, 223\\noptic, 83, 84\\nprincipal, 31\\nsecondary, 35, 36\\nvisual, 81, 82\\nAxonometer, 168, 169\\nB.\\nBand of light, 167, 168\\nBase of prism, 22\\nBeam of light, 11\\nBiconcave lens, 29, 30\\nBiconvex lens, 29, 30\\nBifocals, 272-282\\nBinocular accommodation, 82\\nfixation, 82\\nBlepharitis, 107\\nBrachymetropia, no\\nBriicke, muscle of, 65\\nChromo-aberration test, 143, 144,\\n145, 146\\nCiliary body, 65\\nmuscle, 65\\nanatomy of, 65\\nCobalt-blue glass, 143, 144, 145, 146\\nCocain, 207\\nCompound system, 59, 60\\nConcave lenses, 29, 30\\nmirror, 14, 15\\nin retinoscopy. (See Chap-\\nter VI.)\\nConcomitant squint, 190\\nCondensing lens, 98\\nConic cornea, 132, 170, 171\\nConjugate foci, 33, 34\\nConjunctiva, 200\\nConvergence, 81\\namplitude of, 83\\nangle of, 82\\ninsufficiency of, 83\\nnegative, 83\\npositive, 83\\nrange of, 83\\nConvergent strabismus, 189\\nConvex lenses, 29\\nCoquilles, 204\\nCornea, 120\\nCover chimney, 77\\ntest, 179\\nCramp of accommodation, 210, 211,\\n255, 256, 257\\nCretes prism, 183\\nCrossed diplopia, 177, 1 90\\nCrystalline lens, 21, 67\\nCycloplegia, 208, 209, 210\\nCycloplegics, 200-208\\nCylindric lenses, 42, 43, 44, 222, 223\\naction of, 43, 44, 55, 56\\naxis of, 43\\nneutralization of, 55, 56, 57\\nC.\\nCamera, 64\\nCapsule, 67\\nCardinal points, 59? 60\\nCataract, 267\\nCatoptrics, 9\\nCenter of fixation, 82, 84\\nof rotation, 82\\nCentering of lenses, 53? 54\\nChalazion, 12\\nChoroid, 92, 93\\nD.\\nDark glasses, 204\\nroom, 89, 157\\nDaturin, 201\\nDecentering lenses, 283, 284\\nDe Schweinitz, 185\\nDeviation, angle of, 23\\nin strabismus, 193, 194, 195\\nDiopter, 40, 150\\nDioptrics, 9", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0304.jp2"}, "305": {"fulltext": "INDEX.\\n297\\nDioptric system, 40, 41\\nDiplopia, 28\\ncorrection of, 28\\nDirect method, 88, 151, 152\\nDisc, optic, 91, 151\\nperforated, 139, 140\\npin-hole, 46, 255\\nPlacido s, 132\\nshape of optic, 15 1\\nDistant type, 73, 74, 75\\nDivergence, 82, 189, 190\\nDivergent strabismus, 189, 190\\nDuboisin, 201\\nDynamic refraction, 224, 225\\nElasticity of lens, 66, 67\\nElectric-light blindness, 212\\nElongation of eyeball, 227, 228, 229.\\nEmergent ray, 10\\nEmmetropia, 101, 102, 165, 166\\ndescription of, 101, 102, 103\\nErect image, 94, 95, 96\\nEsophoria, 177, 180, 181\\ndiagnosis of, 180, 181\\ntreatment for, 183-187\\nEsotropia, 177, 189\\ndiagnosis of, 191-195\\ntreatment for, 195\u00e2\u0080\u0094199\\nExercises with prisms, 185, 186, 187\\nExophoria, 177, 180, 181, 257, 258\\ndiagnosis of, 180, 181\\ntreatment for, 183-187\\nExotropia, 177, 190\\ndiagnosis of, 191-195\\ntreatment for, 195-199\\nEye, 58\\ndrops, 200\\nemmetropic, 1 01\\n-glasses, 281\\nhyperopic, 104, 105\\nmyopic, no\\nschematic, 101, 154\\nstandard, 58, 10 1\\n-strain, 211-215\\nFace, asymmetry of, 128\\nFacial illumination, 160\\nFar point, 67, 68\\nFinger exercise, 185\\nFitting of spectacles. (See Chapter\\nXII.)\\nFocal interval, 32\\nlength, 32\\npoints, 121\\nFocus, 11\\nanterior, 59, 60\\nconjugate, 34\\nnegative, 11, 35\\nordinary, 34\\npositive, n\\nposterior, 60\\nprincipal, 32, 59\\nreal, 1 1\\nvirtual, II\\nForm of retinal illumination, 163\\nFormation of images, 37, ^S, 39\\nFox, 272\\nGlass, crown, 21\\nflint, 21\\nGlasses. (See Lenses.)\\nGlaucoma, 203, 267\\nGould, 75, 185, 197, 274\\nGreen, 137\\nH.\\nHelmholtz, 58, IOI\\nHeredity, 105\\nHeteronymous images, 1 74\\nHeterophoria, 177, 179-185\\nHistory, 216, 217, 218\\nHomatropin, 201, 203, 205, 206, 207\\nHomonymous images, 173\\nHow to refract. (See Chapter IX.)\\nHyoscyamin, 201\\nHyperesophoria, 177\\nHypermetropia, 104\\nHyperopia, 104, 155, 166, 233\\nabsolute, 106\\nacquired, 266, 267\\namount of, 1 19\\naxial, 104, 232\\ncauses of, 106\\ndescription of, 104, 1,05, 106\\ndiagnosis of, 109, no\\nestimation of, 1 19\\nfacultative, 106, 236\\nlatent, 106, 236\\nlength of eyeball in, 119", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0305.jp2"}, "306": {"fulltext": "298\\nINDEX.\\nHyperopia, manifest, 106\\nrelative, 106, 236\\nsymptoms of, 107, 232\\ntotal, 106, 236\\ntreatment of, 225, 226, 232, 233,\\n234\\nHyperopic astigmatism, 125, 126\\nHyperphoria, 174, 175, 177, 1 8 1,\\n188\\nHypertropia, 177\\nJackson, 201\\nK.\\nKeratoscope, 132\\nI.\\nIlliterate card, 74\\nIlliterates, 74, 155\\nIlluminated area. (See Figs. 81, 82,\\nand 83.)\\nIllumination, 89\\nfacial, 160\\nretinal, 160\\nImages, 172\\ncrossed, 174\\nformation of, 37, 38, 39\\nformed by mirrors, 13, 14, 15, 16\\nheteronymous, 174\\nhomonymous, 173\\nin astigmatism, 121-127\\nin emmetropia, 64, 99, 100\\nin hyperopia, 64\\nin myopia, 64\\ninverted, 98, 119\\non cornea, 160\\non lens, 160\\nreal, 37\\nretinal, 62, 63\\nvirtual, 37\\nImbalance, 177\\nInch system, 40, 41, 42\\nIndex of refraction, 19, 20, 21\\nIndirect method, 98, 1 19, 152, 153,\\n252\\nInfinity, 67\\nInfraduction, 176\\nInsufficiencies, 178-186\\nInterval, focal, 121, 122\\nof Sturm, 121, 122\\nInversion, 13\\nIris in accommodation, 67\\nin hyperopia, 109\\nin myopia, 115\\nIrregular astigmatism of the cornea,\\n122, 123\\nof the lens, 122, 123\\nLength of eyeball, 119\\nin emmetropia, 119\\nin hyperopia, 1 19\\nin myopia, 1 19\\nin standard eye, 1 19\\nLens, crystalline, 21\\nLenses, 28, 285, 286\\nacromatic, 275, 276\\naction of, 30, 31, 32\\nastigmatic, 121\\nbiconcave, 29, 30\\nbiconvex, 29\\nbifocal, 272-280\\ncollective, 29\\ncombination of, 46-52\\ncylindric, 42, 43, 44\\ndecentered, 283, 284\\ndioptric, 40, 41, 42\\ninch, 40, 41, 42\\nmagnifying, 29\\nmeniscus, 29, 30\\nminifying, 29, 30\\nnegative, 29\\nnumeration of, 40, 41\\nperimetric, 283\\nperiscopic, 29\\nplanoconcave, 29, 30\\nprismatic, 28\\nspheric, 29\\nspherocylindric, 44\\ntinted, 204\\ntoric, 278\\nLigamentum pectinatum, 65\\nLight, 9, 89, 157, 230\\nand shade, 77\\nintensity of, 9\\n-screen, 157\\nsense, 77\\nvelocity of, 9\\nLorgnettes, 278\\nLoring, 86", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0306.jp2"}, "307": {"fulltext": "INDEX.\\n299\\nM.\\nMaddox rod, 182\\nMalingerer, 27\\nManifest refraction, 224, 225\\nMeniscus, 29, 30\\nMeter, 40\\nangle, 82\\nMetric system, 40\\nMires, 147, 150\\nMirror, 13\\nconcave, 14, 15, 157\\nconvex, 16, 17\\nplane, 13, 14, 157\\nreflection from, 13, 14, 15\\nMixed astigmatism, 126, 127\\nMovements of mirror, 159, 160\\nMulatto, 91\\nMuscles. (See Chapter VII.)\\nciliary, 65\\nMydriatics, 200\\nMyopia, no, 166, 236\\naxial, no, 116, 239\\ncauses of, 112, 113, 114\\ndescription of, no, ill, 1 1 2,\\n239\\ndiagnosis of, 115, 116, 237, 238\\nestimation of, 119, 238\\nimage in, 64\\nlength of eyeball in, 119\\nophthalmoscopic appearances in,\\n228, 229\\nprogressive, 227, 228, 229\\nsymptoms of, 114, 115, 238\\ntreatment of, 227, 228, 229, 230,\\n238, 239\\nN.\\nNear point, 68\\ndetermining the, 78, 81\\nNebula, 193\\nNegative aberration, 171\\nangle, 83\\nNerve, optic, 92\\ncolor of, 92\\nshape of, in astigmatism, 15 1\\nsize of, in hyperopia, 95\\nin myopia, 96\\nNettleship, 119\\nNeutralizing lenses, 40, 41, 164, 165\\nNodal points, 35, 36\\nNystagmus, 155\\nO.\\nObserver, 89\\nOccupation, 216\\nOcular gymnastics, 185, 186, 187, 258\\nOpacities, 132\\nOphthalmometer, 147, 148, 149, 150,\\n151\\nOphthalmoplegia, 208\\nOphthalmoscope, 86-100, 151, 152\\nhow to use, 88\\nOptic axis, 83\\ncenter, 35, 36, 53, 54\\ndisc, 92\\nOptics, 9\\nOrbit, 113\\nOrthophoria, 177\\nOrthotropia, 177\\nP.\\nParalysis of accommodation, 208\\ncauses of, 209\\ntreatment of, 210, 211\\nPencil, converging, II\\ndiverging, 1 1\\nPerimeter, 195\\nPeriodic squint, 189, 190\\nPetit s canal, 66\\nPhenomena of light, 1 1\\nPhorometer, 184\\nPhorometry, 175\\nPinc-nez, 281\\nPin-hole disc, 46, 255\\nPlacido s disc, 132, 133, 255\\nPointed line test, 139\\nPoints, cardinal, 58, 59, 60\\nnodal, 35, 36\\nof reversal, 161\\nprincipal, 58, 59, 60\\nPray s letters, 140\\nPresbyopia, 260\\nage of, 260, 261\\ncauses of, 261\\ndescription of, 260, 261\\ndiagnosis of, 262\\nglasses for, 263-267\\nsymptoms of, 262\\nPrescription writing, 52, 53\\nPrincipal axis, 31\\nfocus, 32, 59\\npoints, 58, 59, 60\\nPrism-diopters, 25", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0307.jp2"}, "308": {"fulltext": "300\\nINDEX.\\nPrism exercises, 185, 186, 187, 258\\nrotary, 183\\nWollaston, 147\\nPrisms, 22, 28\\naction of, 22, 23, 24\\ncentrads, 24\\nneutralization of, 25, 26, 27\\nnumeration of, 24, 25\\nuses of, 27, 28, 185\\nPunctum proximum, 68\\ndetermination of the, J\\nin emmetropia, 68\\nin hyperopia, 71\\nin myopia, 72\\nremotum, 67\\ndetermination of the, 75, 76\\nin emmetropia, 68\\nin hyperopia, 70, 71\\nin myopia, 71, 72\\nnegative, 105\\npositive, 71\\nPupil, size of, in emmetropia, 10\\nin hyperopia, 109\\nin myopia, 1 15\\nR.\\nRandall, 73\\nRange of accommodation, 68\\nin emmetropia, 68, 69, 70\\nin hyperopia, 70, 7 1\\nin myopia, 71, J 2\\nof convergence, 83\\nRays, 10\\nconvergent, 1 1\\ndivergent, 10\\nemergent, 10\\nincident, 10\\nparallel, 10\\nreflected, 10\\nrefracted, 10\\nReflection, 12\\nby mirrors, 1 3- 1 7\\nlaws of, 12\\nRefraction, 17\\napplied. (See Chapter X.)\\nby cylinders, 43, 44, 222, 223\\nby prisms, 23, 24\\nby spheres, 31, 221, 222\\nhow to refract. (See Chapter\\nIX.)\\nindex of, 19, 20\\nlaws of, 18\\nRegular astigmatism. (See Astigma-\\ntism.\\nRetina, 92\\nRetinal asthenopia. (See Asthen-\\nopia.\\nillumination, 160\\nimage in astigmatism, 1 21\\nin emmetropia, 64\\nin hyperopia, 64\\nin myopia, 64\\nRetinoscopy. (See Chapter VI.)\\nRisley, 115, 183\\nRod test, 182\\nRods and cones, 73\\nRoom, 89, 157\\nS.\\nScheiner s test, 140-143\\nSchematic eye, 58, 154\\nScissor movement, 170\\nScopolamin, 201, 203\\nSecond sight, 265\\nShadow test. (See Chapter VI.)\\nShadows in retinoscopy, 161\\nSimple hyperopic astigmatism, 124,\\nmyopic astigmatism, 125\\nSnellen, 73\\nSnow-blindness, 212\\nSpasm of the accommodation, 210,\\n211\\ncauses, 210\\nsymptoms, 211\\ntreatment of, 211, 256, 257\\nclonic, 210, 211\\ntonic, 210, 211, 255, 256, 257\\nSpectacles, 280, 281, 285, 286, 287,\\n288\\nfor adults, 280, 281\\nfor aphakia, 272\\nfor astigmatism, 281\\nfor children, 280\\nfor hyperopia, 281\\nfor myopia, 281\\nfor presbyopia, 272\\nfor strabismus, 281\\nmeasurements for, 288, 289, 290,\\n291\\nSquint, 189. (See Strabismus.)\\nStandard eye, 58\\nStatic refraction, 224, 225\\nStenopeic slit, 46, 133, 134", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0308.jp2"}, "309": {"fulltext": "INDEX.\\n301\\nStevens, 177, 184\\nStrabismonieter, 194\\nStrabismus, 189\\nalternating, 189, 190\\namount of, 193, 194, 195\\nangle of, 194\\napparent angle of, 194, 195\\nconcomitant, 189\\nconstant, 189\\nconvergent, 189\\ndivergent, 189, 190\\nmonolateral, 189, 190\\nparalytic, 189, 190\\nperiodic, 189, 190\\ntreatment of, 195-199\\nvertical, 190\\nSturm, interval of, 121, 122\\nSupraduction, 176\\nSurfaces of cylinders, 42\\nof mirrors, 14\\nof prisms, 22\\nof spheres, 29\\nSymptoms of aphakia, 267\\nof asthenopia, 211\\nof astigmatism, 131\\nof hyperopia, 107, 108\\nof myopia, 114, 115\\nof presbyopia, 262\\nT.\\nTable of amplitude of accommoda-\\ntion, 69\\nof axial length of eyeball, 119\\nof indexes, 21\\nof near points, 69\\nof prisms, 26\\nTargets, 147, 148, 150\\nTenotomy, 188, 189, 199\\nTest for aphakia, 267\\nfor astigmatism, 131\\nfor hyperopia, 69\\nfor malingering, 27\\nfor muscles. (See Chapter VII.\\nfor myopia, 69\\nfor near point, 68\\nfor vision, 62\\n-letters, 73, 74\\n-type, 73, 74, 78, 79, 80\\nThomson s ametrometer, 146, 147\\nTinted glasses, 283\\nTrial-case, 44, 45\\nTrial-frames, 45, 46, 47\\nTrifocals, 283\\nV.\\nVacuum, 19, 20\\nVirtual focus, 15, 17\\nimages, 15, 17\\nVision, acuteness of, 61\\nbinocular, 172\\ndetermination of, 72, 73\\nVisual acuity, 62, 63\\nnormal, 61\\nangle, 60\\naxis, 81, 82\\nW.\\nWallace, 74", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0309.jp2"}, "310": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0310.jp2"}, "311": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0311.jp2"}, "312": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0312.jp2"}, "313": {"fulltext": "NO. 8 JULY, 1900\\nA Classified Catalogue of\\nBooks on Medicine and the\\nCollateral Sciences, Phar-\\nmacy, Dentistry, Chemistry,\\nHygiene, Microscopy, Etc.\\nejt\\nP. Blakiston s Son Company, Pub-\\nlishers of Medical and Scientific Books,\\n1012 Walnut Street, Philadelphia", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0313.jp2"}, "314": {"fulltext": "SUBJECT INDEX\\nSpecial Catalogues of Books on Pharmacy, Dentistry,\\nChemistry, Hygiene, and Nursing will be sent free upon\\napplication. All inquiries regarding prices, dates of edition,\\nterms,- etc., will receive prompt attention.\\nSUBJECT PAGE\\nAlimentary Canal(seeSurgery) 19\\nAnatomy 3\\nAnesthetics 14\\nAutopsies (see Pathology) 16\\nBacteriology (see Pathology) 16\\nBandaging (see Surgery) 19\\nBlood, Examination of 16\\nBrain 4\\nChemistry 4\\nChildren, Diseases of 6\\nClimatology 14\\nClinical Charts 6\\nCompends 22, 23\\nConsumption (see Lungs) H\\nCyclopedia of Medicine 8\\nDentistry 7\\nDiabetes (see Urin. Organs).. 21\\nDiagnosis 17\\nDiagrams (see Anatomy) 3\\nDictionaries, Cyclopedias 8\\nDiet and Food 14\\nDissectors 3\\nEar 9\\nElectricity 9\\nEmergencies (see Surgery) 19\\nEye 9\\nFevers 9\\nGout 10\\nGynecology 21\\nHay Fever 20\\nHeart 10\\nHistology 10\\nHospitals (see Hygiene) 11\\nHydrotherapy... 14\\nHygiene 11\\nInsanity 4\\nLatin, Medical (see Miscella-\\nneous and Pharmacy) 14, 16\\nLife Insurance 14\\nLungs 12\\nMassage 12\\nMateria Medica 12\\nMedical Jurisprudence 13\\nMicroscopy 13\\nM ilk Analysis (see Chem istry) 4\\nSUBJECT. PAGE\\nMiscellaneous 14\\nNervous Diseases 14\\nNose 20\\nNursing 15\\nObstetrics 16\\nOphthalmology 9\\nOrganotherapy 14\\nOsteology (see Anatomy) 3\\nPathology 16\\nPharmacy 16\\nPhysical Diagnosis 17\\nPhysical Training (see Miscel-\\nlaneous) 14\\nPhysiology 17\\nPneumotherapy 14\\nPoisons (see Toxicology) 13\\nPopular Medicine 10\\nPractice of Medicine 18\\nPrescription Books 18\\nRefraction (see Eye) 9\\nRheumatism 10\\nSanitary Science 11\\nSkin 19\\nSpectacles (see Eye) 9\\nSpine (see Nervous Diseases) 14\\nStomach (see Miscellaneous)... 14\\nStudents Compends 22, 23\\nSurgery and Surgical Dis-\\neases 19\\nSyphilis 21\\nTechnological Books 4\\nTemperature Charts 6\\nTherapeutics 12\\nThroat 20\\nToxicology 13\\nTumors (see Surgery).. 19\\nU. S. Pharmacopoeia... 16\\nUrinary Organs 20\\nUrine 20\\nVenereal Diseases 21\\nVeterinary Medicine 21\\nVisiting Lists, Physicians\\n{Send for Special Circular.)\\nWater Analysis 11\\nWomen, Diseases of. 21\\nggT 5 The prices as given in this Catalogue are net. Cloth\\nbinding, unless otherwise specified. Tjslpaid, upon receipt\\nof advertised price.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0314.jp2"}, "315": {"fulltext": "SUBJECT CATALOGUE OF MEDICAL BOOKS. 3\\nSPECIAL NOTE.\u00e2\u0080\u0094 The prices given in this catalogue are\\nabsolutely net, no discount can be allowed retail purchasers under any\\nconsideration. This rule has been estab ished in order that everyone\\nwill be treated alike, a general reduction in former prices having been\\nmade to meet previous reta.l discounts. Upon receipt of the advertised\\nprice any book will be forwarded by mail or express, all charges\\nprepaid.\\nANATOMY.\\nMORRIS. Text-Book ot Anatomy. 2d Edition. Revised and\\nEnlarged. 790 Illustrations, 214 of which are printed in coiors.\\nCloth, $6.00; Leather, $7. 00; Half Russia, #8.00\\nThe ever-growing popularity of the book with teachers and students\\nis an index of its value, and it may safely be recommended to all inter-\\nested. Medical Record, New York.\\nJ 3f Sample pages and illustrations will be sent free to any address.\\nBROOMELL. Anatomy and Histology of the Human Mouth\\nand Teeth. 284 Illustrations. $4 50\\nDEAVER. Surgical Anatomy. A Treatise on Human Anatomy\\nin its Application to Medicine and Surgery. With about 400 very\\nHandsome full-page Illustrations Engraved from Original Drawings\\nmade by special Art sts from dissections prepared for the purpose.\\nThree Volumes. Royal Square Octavo\\nCloth, $21 00 Half Morocco or Sheep, $24.00 Half Russia, $27 00\\nECKLEY. Practical Anatomy. A Manual for use in the Dissect-\\ning Room. Based upon Morris Text-Bookof Anatomy and including\\na Section on the Fundamental Principles of Anatomy. With 347\\nIllustrations, many of which are in colors. Cloth, $3 50; Oil Cloth, $4.00\\nGORDINIER. Anatomy of the Central Nervous System.\\nWith 271 Illustrations, many of which are original. Cloth, $6.00\\nHEATH. Practical Anatomy. 8th Edition. 300 Ulus. $4.25\\nHOLDEN. Anatomy. A Manual of the Dissections of the Human\\nBody. Carefully Revised by A. Hewson, m.d., Demonstrator of\\nAnatomy, Jefferson Medical College. Philadelphia. Over 300 hand-\\nsome Illustrations. 7th Edition In two compact i2mo Volumes,\\nLarge New Type. Bound in Oil Cloth, price of each Volume, $1.50\\nHOLDEN. Human Osteology. Comprising a Description of the\\nBones, with Colored Delineations of the Attachments of the Muscles.\\nThe General and Microscopical Structure of Bone and its Develop-\\nment. With Lithographic Plates and numerous Illus. 8th Ed. $5.25\\nHOLDEN. Landmarks. Medical and Surgical. 4 th Ed. $1 00\\nMACALIST\u00c2\u00a3R. Human Anatomy. Systematic and Topograph-\\nical, including the Embryology, Histology, and Morphology of Man.\\nWith Special Reference to the Requirements of Practical Surgery and\\nMedicine. 816 Illustrations. Cloth, $5.00 Leather, $6.00\\nMARSHALL. Physiological Diagrams. Life Size, Colored.\\nEleven Life-Size Diagrams (each seven feet by three feet seven\\ninches). Designed for Demonstration before the Class.\\nIn Sheets, Unmounted, $40.00; Backed with Muslin and Mounted\\non Rollers, $60.00 Ditto, Spring Rollers, in Handsome Walnut Wall\\nMap Case, $100.00; Single Plates Sheets, $5.00; Mounted, $7.50.\\nExplanatory Key, .50. Purchaser must pay freight charges.\\nPOTTER. Compend of Anatomy, Including Visceral Anatomy.\\n6th Ed. 16 Lith. Plates and 117 other Illus. .80 Interleaved, $1.25\\nWILSON. Anatomy, nth Edition. 429 Illus., 26 Plates. $5.00\\nWINDLE. Surface Anatomy. Colored and other Illus. $1.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0315.jp2"}, "316": {"fulltext": "SUBJECT CATALOGUE.\\nBRAIN AND INSANITY (see also\\nNervous Diseases).\\nBLACKBURN. A Manual of Autopsies. Designed for the Use\\nof Hospitals for the Insane and other Public Institutions. Ten full-\\npage Plates and other Illustrations. $125\\nGORDINIER. The Gross and Minute Anatomy of the Central\\nNervous System. With many full-page and other Illustrations.\\n8vo. Cloth, #6.00; Sheep, $7.00\\nGOWERS. Diagnosis of Diseases of the Brain. 2d Edition.\\nIllustrated. $1.50\\nHORSLEY. The Brain and Spinal Cord. The Structure and\\nFunctions of. Numerous Illustrations. $2.50\\nLEWIS (BEVAN). Mental Diseases. A Text Book Having\\nSpecial Reference to the Pathological Aspects of Insanity. 26 Litho-\\ngraphic Plates and other Illustrations. 2d Ed. Just Ready. $7.00\\nMANN. Manual of Psychological Medicine and Allied\\nNervous Diseases. $3-\u00c2\u00b0o\\nREGIS. Mental Medicine. Authorized Translation by H. M.\\nBannister, m.d. $2.00\\nSHUTTLEWORTH. Mentally Deficient Children. New\\nEdition. $1.50\\nSTEARNS. Mental Diseases. With a Digest of Laws Relating\\nto Care of Insane. Illustrated. Cloth, $2.75: Sheep, $3.25\\nTUKE. Dictionary ot Psychological Medicine. Giving the\\nDefinition, Etymology, and Symptoms of the Terms used in Medical\\nPsychology, with the Symptoms, Pathology, and Treatment of the\\nRecognized Forms of Mental Disorders. Two volumes. $10.00\\nWOOD, H. C. Brain and Overwork. .40\\nCHEMISTRY AND TECHNOLOGY.\\nSpecial Catalogue of Chemical Books sent free upon application.\\nALLEN. Commercial Organic Analysis. A Treatise on the\\nModes of Assaying the Various Organic Chemicals and Products\\nEmployed in the Arts, Manufactures, Medicine, etc., with concise\\nmethods for the Detection of Impurities, Adulterations, etc. 8vo.\\nVol. I. Alcohols, Neutral Alcoholic Derivatives, etc., Ethers, Veg-\\netable Acids, Starch, Sugars, etc. 3d Edition, by Henry Leff-\\nMANN, M. D. $4-5\u00c2\u00b0\\nVol. II, Part I. Fixed Oils and Fats, Glycerol, Explosives, etc.\\n3d Edition, by Henry Leffmann, m. d. $3-5o\\nVol. II, Part II. Hydrocarbons, Mineral Oils. Lubricants, Benzenes,\\nNaphthalenes and Derivatives, Creoscte, Phenols, etc. 3d Edition,\\nby Henry Leffmann, m.d. $3-5\u00c2\u00b0\\nVol. II, Part III. Terpenes, Essential Oils, Resins, Camphors, etc.\\n3d Edition, by Henry Leffmann, m.d. Preparing.\\nVol. Ill, Part I. Tannins, Dyes and Coloring Matters. 3d Edition.\\nRevised by J. Merritt Matthews, ph.d., of the Philadelphia\\nTextile School. Illustrated. In Press.\\nVol. Ill, Part II. The Amines, Hydrazines and Derivatives,\\nPyridine Bases. The Antipyretics, etc. Vegetable Alkaloids, Tea,\\nCoffee, Cocoa, etc. 8vo. 2d Edition. $450\\nVol. Ill, Part III. Vegetable Alkaloids, Non-Basic Vegetable Bitter\\nPrinciples. Animal Bases, Animal Acids, Cyanogen Compounds,\\netc. 2d Edition, 8vo. $4-5\u00c2\u00b0\\nVol. IV. The Proteids and Albuminous Principles. 2d Ed. $4.50", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0316.jp2"}, "317": {"fulltext": "MEDICAL BOOKS.\\nALLEN. Albuminous and Diabetic Urine. Illustrated. $2.25\\nBARTLEY. Medical and Pharmaceutical Chemistry. A\\nText-Book for Medical, Dental, and Pharmaceutical Students. With\\nIllustrations, Glossary, and Complete Index. 5th Edition, carefully\\nRevised. Cloth, $3.00 Sheep, $3.50\\nBARTLEY. Clinical Chemistry. The Examination of Feces,\\nSaliva, Gastric Juice, Milk, and Urine. #1.00\\nBLOXAM. Chemistry, Inorganic and Organic. With Experi-\\nments. 8th Ed., Revised. 281 Engravings. Clo., $4-25 Lea., $5.25\\nCALDWELL. Elements of Qualitative and Quantitative\\nChemical Analysis. 3d Edition, Revised. $i-5\u00c2\u00b0\\nCAMERON. Oils and Varnishes. With Illustrations. $2.25\\nCAMERON. Soap and Candles. 54 Illustrations. $2.00\\nGARDNER. The Brewer, Distiller, and Wine Manufac-\\nturer. Illustrated. $i-5\u00c2\u00b0\\nGARDNER. Bleaching, Dyeing, and Calico Printing. $1.50\\nGROVES AND THORP. Chemical Technology. The Appli-\\ncation of Chemistry to the Arts and Manufactures.\\nVol. I. Fuel and Its Applications. 607 Illustrations and 4 Plates.\\nCloth, $5.00; Half Morocco, $6.50\\nVol.11. Lighting. Illustrated. Cloth, #4.00; Half Morocco, $5.50\\nVol. III. Lighting Continued. In Press.\\nVol. I V. Electric Lighting. In Press.\\nHOLLAND. The Urine, the Gastric Contents, the Common\\nPoisons, and the Milk. Memoranda, Chemical and Microscopi-\\ncal, for Laboratory Use. 6th Ed. Illustrated and interleaved, $1.00\\nLEFFMANN. Compend of Medical Chemistry, Inorganic\\nand Organic. Including Urine Analysis. 4th Edition, Rewritten\\nand Revised. .80; Interleaved, $1. 25\\nLEFFMANN. Analysis of Milk and Milk Products. Arranged\\nto Suit the Needs of Analytical Chemists. Dairymen, and Milk Inspec-\\ntors. 2d Edition. Enlarged, Illustrated. $1.25\\nLEFFMANN. Water Analysis. For Sanitary and Technic Pur-\\nposes. Illustrated. 4th Edition. $125\\nLEFFMANN. Structural Formulae. Including 180 Structural\\nand Stereo-Chemical Formulae. i2mo. Interleaved. #1.00\\nMUTER. Practical and Analytical Chemistry. 2d American\\nfrom the Eighth English Edition Revised to meet the requirements\\nof American Students. 56 Illustrations. $1.25\\nOETTEL. Exercises in Electro-Chemistry. Illustrated. .75\\nOETTEL. Electro-Chemical Experiments. Illustrated. .75\\nRICHTER. Inorganic Chemistry. 4th American, from 6th Ger-\\nman Edition. Authorized translation by Edgar F. Smith, m.a.,\\nph.d. 89 Illustrations and a Colored Plate. J -75\\nRICHTER. Organic Chemistry. 3d American Edition. Trans,\\nfrom the 8th German by Edgar F. Smith. Illustrated. 2 Volumes.\\nVol. I. Aliphatic Series. 62s Pages. $3.00\\nVol. II. Carbocyclic Series. 671 Pages. $3.00\\nSMITH. Electro-Chemical Analysis. 2d Edition, Revised. 28\\nIllustrations. $1.25\\nSMITH AND KELLER. Experiments. Arranged for Students\\nin General Chemistry. 3d Edition. Illustrated. .60", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0317.jp2"}, "318": {"fulltext": "SUBJECT CATALOGUE.\\nSUTTON. Volumetric Analysis. A Systematic Handbook for\\nthe Quantitative Estimation of Chemical Substances by Measure,\\nApplied to Liquids, Solids, and Gases. 8th Edition, Revised. 112\\nIllustrations. In Press.\\nSYMONDS. Manual of Chemistry, for Medical Students.\\n2d Edition. #2.00\\nTRAUBE. Physico-Chemical Methods. Translated by Hardin.\\n97 Illustrations. $1.50\\nTHRESH. Water and Water Supplies. 2d Edition. $2.00\\nULZER AND FRAENKEL. Chemical Technical Analysis.\\nTranslated by Fleck. Illustrated. $1.25\\nWOODY. Essentials of Chemistry and Urinalysis. 4th\\nEdition. Illustrated. In Press.\\nSpecial Catalogue of Books on Chemistry free upon application\\nCHILDREN.\\nCAUTLIE. Feeding of Infants and Young Children by Nat-\\nural and Artificial Methods. $2.00\\nHALE. On the Management of Children. .50\\nHATFIELD. Compend of Diseases of Children. With a\\nColored Plate. 2d Edition. .80; Interleaved, $1.25\\nMEIGS. Infant Feeding and Milk Analysis. The Examination\\nof Human and Cow s Milk, Cream, Condensed Milk, etc., and\\nDirections as to the Diet of Young Infants. .50\\nPOWER. Surgical Diseases of Children and their Treat-\\nment by Modern Methods. Illustrated. $2.50\\nSHUTTLEWORTH. Mentally Deficient Children. New\\nEdition. $1-50\\nSTARR. The Digestive Organs in Childhood. The Diseases of\\nthe Digestive Organs in Infancy and Childhood. With Chapters on\\nthe Investigation of Disease and the Management of Children. 2d\\nEdition, Enlarged. Illustrated by two Colored Plates and numerous\\nWood Engravings. $2 00\\nSTARR. Hygiene of the Nursery. Including the General Regi-\\nmen and Feeding of Infants and Children, and the Domestic Manage-\\nment of the Ordinary Emergencies of Early Life, Massage, etc. 6th\\nEdition. 25 Illustrations. $1.00\\nSMITH. Wasting Diseases of Children. 6th Edition. $2.00\\nTAYLOR AND WELLS. The Diseases of Children. Illus-\\ntrated. A New Manual. 746 pages. $400\\nCLINICAL CHARTS.\\nGRIFFITH. Graphic Clinical Chart for Recording Temper-\\nature, Respiration, Pulse, Day of Disease, Date, Age, Sex,\\nOccupation, Name, etc. Printed in three colors. Sample copies\\nfree. Put up in loose packages of fifty, .50. Price to Hospitals, 500\\ncopies, $4.00; 1000 copies, $7.50. With name of Hospital printed\\non, .50 extra.\\nKEEN S CLINICAL CHARTS. Seven Outline Drawings of the\\nBody, on which may be marked the Course of Disease, Fractures,\\nOperations, etc. Pads of fifty, Ji.co. Each Drawing may also be\\nhad separately, twenty-five to pad, 25 cents.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0318.jp2"}, "319": {"fulltext": "MEDICAL BOOKS.\\nSCHREINER. Diet Lists. Arranged in the form of a chart.\\nWith Pamphlets of Specimen Dietaries. Pads of 50. .75\\nDENTISTRY.\\nSpecial Catalogue of Dental Books sent free upon application.\\nBARRETT. Dental Surgery for General Practitioners and\\nStudents of Medicine and Dentistry. Extraction of Teeth,\\netc. 3d Edition. Illustrated. Nearly Ready.\\nBROOMELL. Anatomy and Histology of the Human Mouth\\nand Teeth. 284 Handsome Illustrations. ?4-5Q\\nFLAGG. Plastics and Plastic Filling, as Pertaining to the Filling\\nof Cavities in Teeth of all Grades of Structure. 4th Edition. $4.00\\nFILLEBROWN. A Text-Book of Operative Dentistry.\\nWritten by invitation of the National Association of Dental Facul-\\nties. Illustrated. $2.25\\nGORGAS. Dental Medicine. A Manual of Materia Medica and\\nTherapeutics. 6th Edition, Revised. Cloth, $4.00; Sheep, $5.00\\nHARRIS. Principles and Practice of Dentistry. Including\\nAnatomy, Physiology, Pathology, Therapeutics, Dental Surgery,\\nand Mechanism. 13th Edition. Revised by F. J. S. Gorgas, m.d.,\\nd.d.s. 1250 Illustrations. Cloth, $6.00; Leather, $7.00\\nHARRIS. Dictionary of Dentistry. Including Definitions of Such\\nWords and Phrases of the Collateral Sciences as Pertain to the Art and\\nPractice of Dentistry. 6th Edition. Revised and Enlarged by Fer-\\ndinand F. S. Gorgas, m.d., d.d.s. Cloth, $5.00 Leather, $6.00\\nHEATH. Injuries and Diseases of the Jaws. 4th Edition. 187\\nIllustrations. $4.50\\nHEATH. Lectures on Certain Diseases of the Jaws. 64\\nIllustrations. Boards, .50\\nRICHARDSON. Mechanical Dentistry. 7th Edition. Thor-\\noughly Revised and Enlarged by Dr. Geo. W. Warren. 691 Illus-\\ntrations. Cloth, $5.00; Leather, #6.00\\nSMITH. Dental Metallurgy. Illustrated. $1.75\\nTAFT. Index of Dental Periodical Literature. $2.00\\nTALBOT. Irregularities of the Teeth and Their Treatment.\\n2d Edition. 234 Illustrations. $300\\nTOMES. Dental Anatomy. Human and Comparative. 263 Illus-\\ntrations. 5th Edition. $4.00\\nTOMES. Dental Surgery. 4th Edition. 289 Illustrations. $4.00\\nWARREN. Compend of Dental Pathology and Dental Medi-\\ncine. With a Chapter on Emergencies. 3d Edition. Illustrated.\\n.80; Interleaved, $1.25\\nWARREN. Dental Prosthesis and Metallurgy. 129 Ills. $1.25\\nWHITE. The Mouth and Teeth. Illustrated. .40\\nSpecial Catalogue of Dental Books free upon application.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0319.jp2"}, "320": {"fulltext": "SUBJECT CATALOGUE.\\nDICTIONARIES.\\nGOULD. The Illustrated Dictionary of Medicine, Biology,\\nand Allied Sciences. Being an Exhaustive Lexicon of Medicine\\nand those Sciences Collateral to it: Biology (Zoology and Botany),\\nChemistry, Dentistry, Parmacology, Microscopy, etc., with many\\nuseful Tables and numerous fine Illustrations. 1633 pages. 5th Ed.\\nSheep or Half Dark Green Leather, $10.00; Thumb Index, $11.00\\nHalf Russia, Thumb Index, $12.00\\nGOULD. The Medical Student s Dictionary, nth Edition.\\nIllustrated. Including all the Words and Phrases Generally Used\\nin Medicine, with their Proper Pronunciation and Definition, Based\\non Recent Medical Literature. With a new Table of Eponymic\\nTerms and Tests and Tables of the Bacilli, Micrococci, Mineral\\nSprings, etc., of the Arteries, Muscles, Nerves, Ganglia, Plexuses, etc.\\nnth Edition. Enlarged by over iod pages and illustrated with a\\nlarge number of engravings. 830 paees. Just Ready.\\nHalf Green Morocco, $2.50 Thumb Index, $3 00\\nGOULD. The Pocket Pronouncing Medical Lexicon. 4th Edi-\\ntion. (30,000 Medical Words Pronounced and Defined.) Containing\\nall the Words, their Definition and Pronunciation, that the Medical,\\nDental, or Pharmaceutical Student Generally Comes in Contact\\nWith also Elaborate Tables of Eponymic Terms. Arteries, Muscles,\\nNerves, Bacilli, etc., etc., a Dose List in both English and Metric\\nSystems, etc., Arranged in a Most Convenient Form for Reference and\\nMemorizing. A new (Fourth) Edition, Revised and Enlarged.\\n838 pages. Just Ready.\\nFull Limp Leather, Gilt Edges, $1.00 Thumb Index, $1.25\\n100,000 Copies of Gould s Dictionaries Have Been Sold.\\nGOULD AND PYLE. Cyclopedia of Practical Medicine and\\nSurgery. Seventy-two Special Contributors. Illustrated.\\nOne Volume. A Concise Reference Handbjok, Alphabetically\\nArranged, of Medicine, Surgery, Obstetrics, Materia Medica,\\nTherapeutics, and the Various Specialties, with Particular Reference\\nto Diagnosis and Treatment. Compiled under the Editorial Super-\\nvision of George M. Gould, m.d., Author of An Illustrated\\nDictionary of Medicine Editor Philadelphia Medical Journal,\\netc.; and Walter L. Pyle. m.d., Assistant Surgeon Wills Eye\\nHospital formerly Editor International Medical Magazine, etc.,\\nand Seventy-two Special Contributors. With many Illustrations.\\nLarge Square 8vo, to correspond with Gould s Illustrated Dic-\\ntionary. Just Ready. Fuli Sheep or Half Dark-Green Leather, $io.co\\nWith Thumb Index, $ti.oo; Ha f Russia, Thumb Index, $i2.co net.\\nSample Pages and Illustrations and Descriptive Circulars of\\nGould s Dictionaries and Cyclopedia sent free upon application.\\nHARRIS. Dictionary of Dentistry. Including Definitions of Such\\nWords and Phrases of the Collateral Sciences as Pertain to the Art\\nand Practice of Dentistry. 6th Edition. Revised and Enlarged by\\nFerdinand J. S. Gorgas, m.d., d.d.s. Cloth, $5.00; Leather, $6 00\\nLONGLEY. Pocket Medical Dictionary. With an Appendix,\\ncontaining Poisons and their Antidotes, Abbreviations used in Pre-\\nscriptions, etc. Cloth, .75 Tucks and Pocket, $1.00\\nMAXWELL. Terminologia Medica Polyglotta. By Dr.\\nTheodore Maxwell, Assisted by Others. $3.00\\nThe object of this work is to assist the medical men ot any nationality\\nin reading medical literature written in a language not their own.\\nEach term is usually given in seven languages, viz. English, French,\\nGerman, Italian, Spanish, Russian, and Latin.\\nTREVES AND LANG. German-English Medical Dictionary\\nHalf Russia, $3.25", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0320.jp2"}, "321": {"fulltext": "MEDICAL BOOKS.\\nEAR (see also Throat and Nose).\\nBURNETT. Hearing and How to Keep It. Illustrated. .40\\nDALBY. Diseases and Injuries of the Ear. 4th Edition. 38\\nWood Engravings and 8 Colored Plates. $2.50\\nHOVELL. Diseases of the Ear and Naso-Pharynx. Includ-\\ning Anatomy and Physiology of the Organ, together with the Treat-\\nment of the Affections of the Nose and Pharynx which Conduce to\\nAural Disease. 122 Illustrations. 2d Edition. Preparing.\\nPRITCHARD. Diseases of the Ear. 3d Edition, Enlarged.\\nMany Illustrations and Formulae. $1.50\\nWOAKES. Deafness, Giddiness, and Noises in the Head.\\n4th Edition. Illustrated. #2.00\\nELECTRICITY.\\nBIGELOW. Plain Talks on Medical Electricity and Bat-\\nteries. With a Therapeutic Index and a Glossary. 43 Illustra-\\ntions. 2d Edition. $1.00\\nHEDLEY. Therapeutic Electricity and Practical Muscle\\nTesting. 99 Illustrations. Just Ready. $2.50\\nJACOBI. Electrotherapy. Illustrated. In Press.\\nJONES. Medical Electricity. 3d Edition. 112 Illus. In Press.\\nMASON. Medical Electricity. Numerous Illustrations. .75\\nEYE.\\nA Special Circular of Books on the Eye sent free upon application.\\nDONDERS. The Nature and Consequences of Anomalies of\\nRefraction. With Portrait and Illustrations. Half Morocco, $1.25\\nFICK. Diseases of the Eye and Ophthalmoscopy. Trans-\\nlated by A. B. Hale, m. d. 157 Illustrations, many of which are in\\ncolors, and a glossary. Cloth, $4.50; Sheep, $5.50\\nGOULD AND PYLE. Compend of Diseases of the Eye and\\nRefraction. Including Treatment and Operations, and a Section\\non Local Therapeutics. With Formulas, Useful Tables, a Glossary,\\nand in Illus., several of which are in colors. 2d Edition, Revised.\\nCloth, .80; Interleaved, $1.25\\nGOWERS. Medical Ophthalmoscopy. A Manual and Atlas\\nwith Colored Autotype and Lithographic Plates and Wood-cuts,\\nComprising Original Illustrations of the Changes of the Eye in Dis-\\neases of the Brain, Kidney, etc. 3d Edition. $4.00\\nHARLAN. Eyesight, and How to Care for It. Illus. .40\\nHARTRIDGE. Refraction. 104 Illustrations and Test Types.\\n10th Edition, Enlarged. Just Ready. $1.50\\nHARTRIDGE. On the Ophthalmoscope. 3d Edition. With\\n4 Colored Plates and 68 Wood-cuts. $1.50\\nHANSELL AND REBER. Muscular Anomalies of the Eye.\\nIllustrated. $1.50\\nHANSELL AND BELL. Clinical Ophthalmology. Colored\\nPlate of Normal Fundus and 120 Illustrations. #1.50\\nJESSOP. Manual of Ophthalmic Surgery and Medicine. Col-\\nored Plates and 108 other Illustrations. Cloth, $3.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0321.jp2"}, "322": {"fulltext": "10 SUBJECT CATALOGUE.\\nMORTON. Refraction of the Eye. Its Diagnosis and the Cor-\\nrection of its Errors. 6th Edition. |i.oo\\nOHLEMANN. Ocular Therapeutics. Authorized Translation,\\nand Edited by Dr. Charles A. Oliver. J 1 -75\\nPHILLIPS. Spectacles and Eyeglasses. Their Prescription\\nand Adjustment. 2d Edition. 49 Illustrations. $1.00\\nSWANZY. Diseases of the Eye and Their Treatment. 6th\\nEdition, Revised and Enlarged. 158 Illustrations, 1 Plain Plate,\\nand a Zephyr Test Card. #3.00\\nTHORINGTON. Retinoscopy. 3d Edition. Illustrated. $1.00\\nTHORINGTON. Refraction and How to Refract. 200 Illustra-\\ntions, 13 of which are Colored. 301 pages. Just Ready. #1.50\\nWALKER. Students Aid in Ophthalmology. Colored Plate\\nand 40 other Illustrations and Glossary. $i-5o\\nFEVERS.\\nCOLLIE. On Fevers. Their History, Etiology, Diagnosis, Prog-\\nnosis, and Treatment. Colored Plates. $2.00\\nGOODALL AND WASHBOURN. Fevers and Their Treat-\\nment. Illustrated. $3-\u00c2\u00b0\u00c2\u00b0\\nGOUT AND RHEUMATISM.\\nDUCKWORTH. A Treatise on Gout. With Chromo-lithographs\\nand Engravings. Cloth, $6.00\\nGARROD. On Rheumatism. A Treatise on Rheumatism and\\nRheumatic Arthritis. Cloth, $5.00\\nHAIG. Causation of Disease by Uric Acid. A Contribution to\\nthe Pathology of High Arterial Tension. Headache, Epilepsy, Gout,\\nRheumatism, Diabetes, Bright s Disease, etc. 5th Ed. In Press.\\nHEART.\\nSANSOM. Diseases of the Heart. The Diagnosis and Pathology\\nof Diseases of the Heart and Thoracic Aorta. With Plates and other\\nIllustrations. $6.00\\nTHORNE. The Schott Methods of the Treatment of Chronic\\nHeart Disease. Third Edition. Illustrated. Just Ready. $175\\nHISTOLOGY.\\nSTIRLING. Outlines of Practical Histology. 368 Illustrations.\\n2d Edition. Revised and Enlarged. With new Illustrations. $2.00\\nSTOHR. Histology and Microscopical Anatomy. Translated\\nand Edited by A. Schaper, m.d., Harvard Medical School. Second\\nAmerican from 7th German Edition, Revised and Enlarged. 292\\nIllustrations. $3-\u00c2\u00b0\u00c2\u00b0", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0322.jp2"}, "323": {"fulltext": "MEDICAL BOOKS.\\nHYGIENE AND WATER ANALYSIS.\\nSpecial Catalogue of Books on Hygiene sent free upon application.\\nCANFIELD. Hygiene of the Sick-Room. A Book for Nurses\\nand Others Being a Brief Consideration of Asepsis, Antisepsis, Dis-\\ninfection, Bacteriology, Immunity, Heating, Ventilation, etc. $1.25\\nCOPLIN. Practical Hygiene. A Complete American Text-Pook.\\n138 Illustrations. New Edition. Preparing\\nERNST. Prophylaxis and Personal Hygiene. In Press.\\nHARTSHORNE. Our Homes. Illustrated. .40\\nKENWOOD. Public Health Laboratory Work. 116 Illustra-\\ntions and 3 Plates. $2.00\\nLEFFMANN. Examination of Water for Sanitary and\\nTechnical Purposes. 4th Edition. Illustrated. $1.25\\nLEFFMANN. Analysis of Milk and Milk Products. Illus-\\ntrated. Second Edition. $1 .25\\nLINCOLN. School and Industrial Hygiene. .40\\nMcNEILL. The Prevention of Epidemics and the Construc-\\ntion and Management of Isolation Hospitals. Numerous Plans\\nand Illustrations. $3. 50\\nNOTTER AND FIRTH. The Theory and Practice of Hygiene.\\n10 Plates and 135 other Illustrations. 1034 pages. 8vo. $7.00\\nPARKES. Hygiene and Public Health. By Louis C. Parkes,\\nm.d. 5th Edition. Enlarged. Illustrated. #2.50\\nPARKES. Popular Hygiene. The Elements of Health. A Book\\nfor Lay Readers. Illustrated. $125\\nSTARR. The Hygiene of the Nursery. Including the General\\nRegimen and Feeding of Infants and Children, and the Domestic\\nManagement of the Ordinary Emergencies of Early Life, Massage,\\netc. 6th Edition. 25 Illustrations. $1.00\\nSTEVENSON AND MURPHY. A Treatise on Hygiene. By\\nVarious Authors, in Three Octave Volumes. Illustrated.\\nVol. I, $6.00; Vol. II, $6.00; Vol. Ill, $5.00\\nEach Volume sold separately. Special Circular upon application.\\nTHRESH. Water and Water Supplies. 2d Edition. $2.00\\nWILSON. Hand-Book of Hygiene and Sanitary Science.\\nWiih Illustrations. 8th Edition. $3 00\\nWEYL. Sanitary Relations of the Coal-Tar Colors. Author-\\nized Translation by Henry LEFFMANN, M.D, PH.D. $1.25\\nLUNGS AND PLEURA.\\nHARRIS AND BEALE. Treatment of Pulmonary Consump-\\ntion. $2.50\\nKNOPF. Pulmonary Tuberculosis. Its Msdem Prophylaxis\\nand Treatment in Special Institutions and at Home. Illus. #3 00\\nPOWELL. Diseases of the Lungs and Pleurae, including\\nConsumption. Colored Plates and other Illus. 4th Ed. $4-\u00c2\u00b0o", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0323.jp2"}, "324": {"fulltext": "SUBJECT CATALOGUE.\\nMASSAGE.\\nKLEEN. Hand-Book of Massage. Authorized translation by\\nMussey Hartwell, m.d., ph.d. With an Introduction by Dr. S.\\nWeir Mitchell. Illustrated by a series ot Photographs Made\\nEspecially by Dr. Kleen for the American Edition. $2.25\\nOSTROM. Massage and the Original Swedish Move-\\nments. Their Application to Various Diseases of the Body. A\\nManual for Students, Nurses, and Physicians. Fourth Edition, En-\\nlarged. 105 Illustrations, many of which are original. $1.00\\nMITCHELL AND GULICK. Mechanotherapy. Illus. InPress.\\nWARD. Notes on Massage. Interleaved. Paper cover, $1.00\\nMATERIA MEDICA AND THERA-\\nPEUTICS.\\nBIDDLE. Materia Medica and Therapeutics. Including Dose\\nList, Dietary for the Sick, Table of Parasites, and Memoranda of\\nNew Remedies. 13th Edition, Revised. 64 Illustrations and a\\nClinical Index. Cloth, $4. 00; Sheep, #5.00\\nBRACKEN. Outlines of Materia Medica and Pharmacology. $2.75\\nCOBLENTZ. The Newer Remedies. Including their Synonyms,\\nSources, Methods of Preparation, Tests, Solubilities, Doses, etc.\\n3d Edition, Enlarged and Revised. $1.00\\nCOHEN. Physiologic Therapeutics. Mechanotherapy, Mental\\nTherapeutics, Electrotherapy, Climatology, Hydrotherapy, Pneumo-\\ntherapy, Prophylaxis, Alimentotherapy, etc. In Press.\\nDAVIS. Materia Medica and Prescription Writing. $150\\nGORQAS. Dental Medicine. A Manual of Materia Medica and\\nTherapeutics. 6th Edition, Revised. $4-oo\\nGROFF. Materia Medica for Nurses, with questions for Self Exam-\\nination and a complete Glossary. $1.25\\nHELLER. Essentials of Materia Medica, Pharmacy, and\\nPrescription Writing. #1-50\\nMAYS. Theine in the Treatment of Neuralgia. bound, .50\\nPOTTER. Hand-Book of Materia Medica, Pharmacy, and\\nTherapeutics, including the Action of Medicines, Special Therapeu-\\ntics, Pharmacology, etc., including over 600 Prescriptions and For-\\nmulae. 7th Edition, Revised and Enlarged. With Thumb Index in\\neach copy. Cloth, $5.00; Sheep, #6.00\\nPOTTER. Compend of Materia Medica, Therapeutics, and\\nPrescription Writing, with Special Reference to the Physiologi-\\ncal Action of Drugs. 6th Edition. .80; Interleaved, $1.25", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0324.jp2"}, "325": {"fulltext": "MEDICAL BOOKS. 13\\nSAYRE. Organic Materia Medica and Pharmacognosy. An\\nIntroduction to the Study of the Vegetable Kingdom and the Vege-\\ntable and Animal Drugs. Comprising the Botanical and Physical\\nCharacteristics, Source, Constituents, and Pharmacopeial Prepara-\\ntions, Insects Injurious to Drugs, and Pharmacal Botany. With\\nsections on Histology and Microtechnique, by W. C. Stevens.\\n374 Illustrations, many of which are original. 2d Edition.\\nCloth, $4.50\\nWHITE AND WILCOX. Materia Medica, Pharmacy, Phar-\\nmacology, and Therapeutics. 4th American Edition, Revised by\\nReynold W. Wilcox, m.a., m.d., ll.d., Professor ol Clinical\\nMedicine and Therapeutics at the New York Post-Graduate Medical\\nSchool. Cloth, $3.00; Leather, #3. 50\\nThe care with which Dr. Wilcox has performed his work is con-\\nspicuous on every page, and it is evident that no recent drug possess-\\ning any nieiit has escaped his eye. We believe, on the whole, this is\\nthe best book on Materia Medica and Therapeutics to place in the\\nhands of students, and the practitioner will find it a most satisfactory\\nwork for dai y use. The Clevela?id Medical Gazette.\\nMEDICAL JURISPRUDENCE AND\\nTOXICOLOGY.\\nREESE. Medical Jurisprudence and Toxicology. A Text-Book\\nfor Medical and Legal Practitioners and Students. 5th Edition.\\nRevised by Henry Leffmann, m.d. C1o.,#3.oo; Leather, #3. 50\\nTo the student of medical jurisprudence and toxicology it is in-\\nvaluable, as it is concise, clear, and thorough in every respect. The\\nAmerican Journal o/the Medical Sciences.\\nMANN. Forensic Medicine and Toxicology. Illus. $6.50\\nTANNER. Memoranda of Poisons. Their Antidotes and Tests.\\n7th Edition. .75\\nMICROSCOPY.\\nCARPENTER. The Microscope and Its Revelations. 8th\\nEdition. 800 Illustrations and many Lithographs. Preparing.\\nLEE. The Microtomist s Vade Mecum. A Hand-Book of\\nMethods of Microscopical Anatomy. 887 Articles. 5th Edition,\\nEnlarged. Just Ready. #4-oo\\nREEVES. Medical Microscopy, including Chapters on Bacteri-\\nology, Neoplasms, Urinary Examination, etc. Numerous Illus-\\ntrations, some of which are printed in colors. $2.50\\nWETHERED. Medical Microscopy. A Guide to the Use of the\\nMicroscope in Practical Medicine. 100 Illustrations. $2.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0325.jp2"}, "326": {"fulltext": "14 SUBJECT CATALOGUE.\\nMISCELLANEOUS.\\nBRAMWELL. Ansemia. $2.50\\nBURNETT. Foods and Dietaries. A Manual of Clinical Uiet-\\netics. 2d Edition. $1.50\\nBUXTON. Anaesthetics. Illustrated. 3d Edition. #1.50\\nCOHEN. Organotherapy. In Press.\\nDAVIS. Alimentotherapy. In Press.\\nFEN WICK. Ulcer of the Stomach. 42 Illustrations. $3.50\\nGOULD. Borderland Studies. Miscellaneous Addresses and\\nEssays. i2mo. 82.00\\nGREENE. Medical Examination for Life Insurance. Illus-\\ntrated. In Press.\\nHAIG. Causation of Disease by Uric Acid. A Contribution to\\nthe Pathology of High Arterial Tension, Headache, Epilepsy, Gout,\\nRheumatism, Diabetes, Bright s Disease, etc. 5th Ed. In Press.\\nHAIG. Diet and Food. Considered in Relation to Strength and\\nPower of Endurance. 2d Edition. Just Ready. $1.00\\nHEMMETER. Diseases of the Stomach. Their Special Path-\\nology, Diagnosis, and Treatment. With Sections on Anatomy, Diet-\\netics, Surgery, etc. 2d Edition, Revised and Enlarged. Illustrated.\\nlust Ready. Cloth, #6.00; Sheep, $7.00\\nHENRY. A Practical Treatise on Anemia. Halt Cloth, .50\\nMARSHALL. History of Woman s Medical College of Penn-\\nsylvania, ^-so\\nNEW SYDENHAM SOCIETY S PUBLICATIONS. Circulars\\nupon application. Per Annum, J8.00\\nOSGOOD. The Winter and Its Dangers. .40\\nPACKARD. Sea Air and Sea Bathing. .40\\nPARRISH. Alcoholic Inebriety. $1.00\\nRICHARDSON. Long Life and How to Reach It. .40\\nST. CLAIR. Medical Latin. $1.00\\nTESSIER. Pneumotherapy. In Press.\\nTREVES. Physical Education Its Effects, Methods, Etc. .75\\nTURNBULL. Artificial Anaesthesia. 4 th Edition. Illus. $2.50\\nWEBER AND HINSDALE. Climatology. In Press.\\nWILSON. The Summer and Its Diseases. .40\\nWINTERNITZ. Hydrotherapy. In Press.\\nNERVOUS DISEASES.\\nBEEVOR. Diseases of the Nervous System and their Treat-\\nment. $2.50\\nDERCUM. Rest, Hypmotism, Mental Therapeutics. In Press.\\nGORDINIER. The Gross and Minute Anatomy of the Cen-\\ntral Nervous System. With 271 original Colored and other\\nIllustrations. Cloth, $6 00; Sheep, #7.00\\nGOWERS. Manual of Diseases of the Nervous System. A\\nComplete Text-Book. Revised, Enlarged, and in many parts Re-\\nwritten. With many new Illustrations. Two volumes.\\nVol. I. Diseases of the Nerves and Spinal Cord. 3d Edition, En-\\nlarged. Cloth, $4.00; Sheep, $5.00\\nVol. II. Diseases of the Brain and Cranial Nerves General and\\nFunctional Disease. 2d Edition. Cloth, $4.00; Sheep, $5.00\\nGOWERS. Syphilis and the Nervous System. $1.00\\nGOWERS. Clinical Lectures. A New Volume of Essays on the\\nDiagnosis, Treatment, etc., of Diseases of the Nervous System. $2.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0326.jp2"}, "327": {"fulltext": "MEDICAL BOOKS. 15\\nGOWERS. Epilepsy and Other Chronic Convulsive Diseases.\\n2d Edition. In Press.\\nHORSLEY. The Brain and Spinal Cord. The Structure and\\nFunctions of. Numerous Illustrations. $2.50\\nORMEROD. Diseases of the Nervous System. 66 Wood En-\\ngravings. #1.00\\nOSLER. Chorea and Choreiform Affections. $2.00\\nPRESTON. Hysteria and Certain Allied Conditions. Their\\nNature and Treatment. Illustrated. $2.00\\nWOOD. Brain Work and Overwork. .40\\nNURSING (see also Massage).\\nSpecial Catalogue of Books for Nurses sent free upon application.\\nBROWN. Elementary Physiology for Nurses. .75\\nCANFIELD. Hygiene of the Sick-Room. A Book for Nurses and\\nOthers. Being a Brief Consideration of Asepsis, Antisepsis, Disinfec-\\ntion, Bacteriology, Immunity, Heating and Ventilation, and Kindred\\nSubjects for the Use of Nurses and Other Intelligent Women. \u00c2\u00a31.25\\nCUFF. Lectures to Nurses on Medicine. New Edition. $1.25\\nDOMVILLE. Manual for Nurses and Others Engaged in At-\\ntending the Sick. 8th Edition. With Recipes for Sick-room Cook-\\nery, etc. .75\\nFULLERTON. Obstetric Nursing. 41 Ills. 5th Ed. $1.00\\nFULLERTON. Surgical Nursing. Comprising the Regular\\nCourse of Instruction at the Training-School of the Woman s Hos-\\npital, Philadelphia. 3d Edition. 69 Illustrations. $1.00\\nGROFF. Materia Medica for Nurses. With Questions for Self-Ex-\\namination and a very complete Glossary. $1.25\\nIt will undoubtedly prove a valuable aid to the nurse in securing a\\nknowledge of drugs and their uses. The Medical Record, New\\nYork.\\nHORWITZ. Duties of the Surgical Nurse. In Press.\\nHUMPHREY. A Manual for Nurses. Including General\\nAnatomy and Physiology, Management of the Sick Room, etc.\\n17th Ed. Illustrated. $1.00\\nIn the fullest sense, Dr. Humphrey s book is a distinct advance on\\nall previous manuals. It is, in point of fact, a concise treatise on\\nmedicine and surgery for the beginner, incorporating with the text the\\nmanagement of childbed and the hygiene of the sick-room. Its value\\nis greatly enhanced by copious wood -cuts and diagrams of the bones\\nand internal organs. British Medical Journal, London.\\nSTARR. The Hygiene of the Nursery. Including the General\\nRegimen and Feeding of Infants and Children, and the Domestic Man-\\nagement of the Ordinary Emergencies of Early Life, Massage, etc. 6th\\nEdition. 25 Illustrations. $1.00\\nTEMPERATURE AND CLINICAL CHARTS. See page 6.\\nVOSWINKEL. Surgical Nursing. Second Edition, Enlarged.\\n112 Illustrations. $1.00\\nWESTLAND. The Wife and Mother. $1.50", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0327.jp2"}, "328": {"fulltext": "16 SUBJECT CATALOGUE.\\nOBSTETRICS.\\nCAZEAUX AND TARNIER. Midwifery. With Appendix by\\nMund6. The Theory and Practice of Obstetrics, including the Dis-\\neases ot Pregnancy and Parturition, Obstetrical Operations, etc.\\n8th Edition. Illustrated by Chromo- Lithographs, Lithographs, and\\nother full-page Plates, seven of which are beautifully colored, and\\nnumerous Wood Engravings. Cloth, $4.50 Full Leather, 15.50\\nDAVIS. A Manual of Obstetrics. 3d Edition. Preparing.\\nLANDIS. Compend of Obstetrics. 6th Edition, Revised by Wm.\\nH. Wells, Assistant Demonstrator ot Clinical Obstetrics, Jefferson\\nMedical College. With 47 Illustrations, .80; Interleaved, $1.25.\\nWINCKEL. Text-Book of Obstetrics, Including the Pathol-\\nogy and Therapeutics of the Puerperal State. Authorized\\nTranslation by J. Clifton Edgar, a.m., m.d. With nearly 200 Illus-\\ntrations. Cloth, $5.00 Leather, $6.00\\nFULLERTON. Obstetric Nursing. 5th Ed. Illustrated. $1.00\\nPATHOLOGY.\\nBARLOW. General Pathology. 795 pages. 8vo. $5.00\\nBLACK. Micro-Organisms. The Formation of Poisons. .75\\nBLACKBURN. Autopsies. A Manual of Autopsies Designed for\\nthe Use ot Hospitals for the Insane and other Public Institutions.\\nTen full-page Plates and other Illustrations. $1.25\\nCOPLIN. Manual of Pathology. Including Bacteriology, Technic\\nof Post-Mortems, Methods of Pathologic Research, etc. 330 Illus-\\ntrations, 7 Colored Plates, many of which are original. 3d Edition.\\nJust Ready. $3.50\\nDA COSTA. Clinical Pathology of the Blood. Ilius. In Press.\\nGILLIAM. Pathology. A Hand-Book for Students. 47 Illus. .75\\nHEWLETT. Manual of Bacteriology. 75 Illustrations. $3.00\\nKIRKBRIDE. Compend of General Pathology. Illustrated.\\nPreparing.\\nVIRCHOW. Post-Mortem Examinations. A Description and\\nExplanation of the Method of Performing Them in the Dead House\\nof the Berlin Charity Hospital, with Special Reference to Medico-\\nLegal Practice. 3d Edition, with Additions. .75\\nWHITACRE. Laboratory Text-Book of Pathology. With\\n121 Illustrations. l -5\u00c2\u00b0\\nWILLIAMS. Bacteriology. A Manual for Students. 78 Illus-\\ntrations. $1-50\\nPHARMACY.\\nSpecial Catalogue of Books on Pharmacy sent free upon application.\\nCOBLENTZ. Manual of Pharmacy. A Complete Text-Book\\nby the Professor in the New York College of Pharmacy. 2d Edition,\\nRevised and Enlarged. 437 Illus. Cloth, $3.50; Sheep, $4. 50\\nBEASLEY. Book of 3100 Prescriptions. Collected from the\\nPractice of the Most Eminent Physicians and Surgeons English,\\nFrench, and American. A Compendious History ot the Materia\\nMedica, Lists of the Doses of all the Officinal and Established Pre-\\nparations, an Index of Diseases and their Remedies. 7th Ed. $2.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0328.jp2"}, "329": {"fulltext": "MEDICAL BOOKS. 17\\nBEASLEY. Druggists General Receipt Book. Comprising\\na Copious Veterinary Formulary, Recipes in Patent and Proprietary\\nMedicines, Druggists Nostrums, etc. Perfumery and Cosmetics,\\nBeverages, Dietetic Articles and Condiments, Trade Chemicals,\\nScientific Processes, and many Useful Tables, ioth Ed. #2.00\\nBEASLEY. Pharmaceutical Formulary. A Synopsis of the\\nBritish, French, German, and United States Pharmacopoeias. Com-\\nprising Standard and Approved Formulae for the Preparations and\\nCompounds Employed in Medicine. 12th Edition. $2,00\\nPROCTOR. Practical Pharmacy. Lectures on Practical Phar-\\nmacy. With Wood Engravings and 32 Lithographic Fac-simile\\nPrescriptions. 3d Edition, Revised, and with Elaborate Tables of\\nChemical Solubilities, etc. $3.00\\nROBINSON. Latin Grammar of Pharmacy and Medicine.\\n3d Edition. With elaborate Vocabularies. I -75\\nSAYRE. Organic Materia Medica and Pharmacognosy. An\\nIntroduction to the Study of the Vegetable Kingrdom and the Vege-\\ntable and Animal Drugs. Comprising the Botanical and Physical\\nCharacteristics, Source, Constituents, and* Pharmacopeial Prepar-\\nations, Insects Injurious to Drugs, and Parmacal Botany. With\\nsectijns on Histology and Microtechnique, by W. C. Stevens.\\n374 Illustrations. Second Edition. Cloth, #4.50\\nSCOVILLE. The Art of Compounding. Second Edition, Re-\\nvised and Enlarged. Cloth, $2.50\\nSTEWART. Compend of Pharmacy. Based upon Reming-\\nton s Text-Book of Pharmacy. 5th Edition, Revised in Accord-\\nance with the U. S. Pharmacopoeia, 1890. Complete Tables of\\nMetric and English Weights and Measures. .80; Interleaved, $1.25\\nUNITED STATES PHARMACOPOEIA. 7th Decennial Revision.\\nCloth, 32.50 (postpaid, $2.77) Sheep, $3.00 (postpaid, $3.27) Inter-\\nleaved, $4.00 (postpaid. $4.50); Printed on one side of page only,\\nunbound, $3.50 (postpaid, $3.90).\\nSelect Tables from the U. S. P. Being Nine of the Most Impor-\\ntant and Useful Tables, Printed on Separate Sheets. Carefully\\nput up in patent envelope. .25\\nPOTTER. Hand-Book of Materia Medica, Pharmacy, and\\nTherapeutics. 600 Prescriptions. 7th Ed. Clo., $5.00 Sh., $6.00\\nPHYSICAL DIAGNOSIS.\\nBROWN. Medical Diagnosis. A. Manual of Clinical Methods.\\n4th Edition. 1 12 Illustrations. Cloth, $2.25\\nDA COSTA. Clinical Examination of the Blood. Illustrated.\\nIn Press.\\nFENWICK. Medical Diagnosis. 8th Edition. Rewritten and\\nvery much Enlarged. 135 Illustrations. Cloth, $2.50\\nMEMMINGER. Diagnosis by the Urine. 2d Ed. 24 Illus. $1.00\\nTYSON. Hand-Book of Physical Diagnosis. For Students and\\nPhysicians. By the Professor of Clinical Medicine in the University\\nof Pennsylvania. Illus. 3d Ed., Improved and Enlarged. With\\nColored and other Illustrations. $i-5o\\nPHYSIOLOGY.\\nBIRCH. Practical Physiology. An Elementary Class Book.\\n62 Illustrations. I -7S\\nBRUBAKER. Compend of Physiology, ioth Edition, Revised\\nand Enlarged. Illustrated. Just Ready. .80; Interleaved, $1.25\\n2", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0329.jp2"}, "330": {"fulltext": "18 SUBJECT CATALOGUE.\\nKIRKE. Physiology. (16th Authorized Edition. Dark-Red Cloth.)\\nA Hand-Book of Physiology. 16th Edition, Revised, Rearranged,\\nand Enlarged. By Prof. W. D. Halliburton, of Kings College,\\nLondon. 671 Illustrations, some of which are printed in colors.\\nJust Ready. Cloth, $3.00; Leather, $3. 75\\nLANDOIS. A Text-Book of Human Physiology, Including\\nHistology and Microscopical Anatomy, with Special Reference to\\nthe Requirements of Practical Medicine. 5th American, translated\\nfrom the 9th German Edition, with Additions by Wm. Stirling,\\nm.d.,d.sc. 845 Illus., many of which are printed in colors. In Press.\\nSTARLING. Elements of Human Physiology. 100 Ills. $1.00\\nSTIRLING. Outlines of Practical Physiology. Including\\nChemical and Experimental Physiology, with Special Reference to\\nPractical Medicine. 3d Edition. 289 Illustrations. $2.00\\nTYSON. Cell Doctrine. Its History and Present State. $1.50\\nPRACTICE.\\nBEALE. On Slight Ailments; their Nature and Treatment.\\n2d Edition, Enlarged and Illustrated. $1-25\\nFOWLER. Dictionary of Practical Medicine. By various\\nwriters. An Encyclopaedia of Medicine. Clo.,$3.oo; Half Mor. $4.00\\nGOULD AND PYLE. Cyclopedia of Practical Medicine and\\nSurgery. A Concise Reference Handbook, Alphabetically\\nArranged, with particular Reference to Diagnosis and Treatment.\\nEdited by Drs. Gould and Pyle, Assisted by 72 Special Con-\\ntributors. Illustrated, one volume. Large Square Octavo, Uniform\\nwith Goul i s Illustrated Dictionary. Just Beady.\\nSheep or Half Morocco, 0.00: with Thumb Index, $11.00\\nHalf Russia, Thumb Index, $12.00\\n$g= Complete descriptive circular with sample pages and illustra-\\ntions of this book will be sent free upon application.\\nHUGHES. Compend of the Practice of Medicine. 6th Edition,\\nRevised and Enlarged. Just Ready.\\nPart I. Continued, Eruptive, and Periodical Fevers, Diseases of the\\nStomach, Intestines, Peritoneum, Biliary Passages, Liver, Kid-\\nneys, etc., and General Diseases, etc.\\nPart II. Diseases of the Respiratory System, Circulatory System,\\nand Nervous System; Diseases of the Blood, etc.\\nPrice of each part, .80; Interleaved, $1.25\\nPhysician s Edition. In one volume, including the above two\\nparts, a Section on Skin Diseases, and an Index. 6th Revised\\nEdition. 625 pp. Just Ready. Full Morocco, Gilt Edge, $2.25\\nTAYLOR. Practice of Medicine. 5th Edition. Cloth, $4.00\\nTYSON. The Practice of Medicine. By James Tyson, m.d.,\\nProfessor of Medicine in the University of Pennsylvania. A Com-\\nplete Systematic Text-book with Special Reference to Diagnosis and\\nTreatment. Illustrated. 8vo.\\nCloth, $5.50; Leather, $6.50; Half Russia, $7.50\\nPRESCRIPTION BOOKS.\\nBEASLEY. Book of 3100 Prescriptions. Collected from the\\nPractice of the Most Eminent Physicians and Surgeons English,\\nFrench, and American. A Compendious History of the Materia,\\nMedica, Lists of the Doses of all Officinal and Established Prepara-\\ntions, and an Index of Diseases and their Remedies. 7th Ed. $2.00", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0330.jp2"}, "331": {"fulltext": "MEDICAL BOOKS. 19\\nBEASLEY. Druggists General Receipt Book. Comprising\\na Copious Veterinary Formulary, Recipes in Patent and Proprie-\\ntary Medicines, Druggists Nostrums, etc. Perfumery and Cos-\\nmetics, Beverages, Dietetic Articles and Condiments, Trade Chem-\\nicals, Scientific Processes, and an Appendix of Useful Tables.\\n10th Edition, Revised. $2.00\\nBEASLEY. Pocket Formulary. ASynopsisof the British, French,\\nGerman, and United States Pharmacopoeias and the chief unofficial\\nFormularies. 12th Edition. $2.00\\nSKIN.\\nBULKLEY. The Skin in Health and Disease. Illustrated. .40\\nCROCKER. Diseases of the Skin. Their Description, Pathol-\\nogy, Diagnosis, and Treatment, with Special Reference to the Skin\\nEruptions of Children. 92 Illus. 3d Edition. Preparing.\\nIMPEY. Leprosy. 37 Plates. 8vo. \u00c2\u00a33.50\\nSCHAMBERG. Diseases of the Skin. 2d Edif on. ico Illus-\\ntrations. Being No. 16 Quiz-Compend Series. Just Ready.\\nCloth, .80; Interleaved, $1.25\\nVAN HARLINGEN. On Skin Diseases. A Practical Manual\\nof Diagnosis and Treatment, with special reference to Differential\\nDiagnosis. 3d Edition, Revised and Enlarged. With Formulae\\nand 60 Illustrations, some of which are printed in colors. 12.75\\nSURGERY AND SURGICAL DIS-\\nEASES (see also Urinary Organs).\\nBUTLIN. Operative Surgery of Malignant Disease. 2d Edi-\\ntion. Illustrated. Octavo. Just Ready. $4-5\u00c2\u00b0\\nCRIPPS. Ovariotomy and Abdominal Surgery. Illus. $8.00\\nDEAVER. Surgical Anatomy. A Treatise on Human Anatomy\\nin its Application to Medicine and Surgery. With about 400 very\\nHandsome full-page Illustrations Engraved from Original Drawings\\nmade by special Artists from Dissections prepared for the purpose.\\nThree Volumes. Royal Square Octavo.\\nCloth, $21. co Half Morocco or Sheep, $24.00 Half Russia, $27.00\\nComplete descriptive circular and special terms upon application.\\nDEAVER. Appendicitis, Its Symptoms, Diagnosis, Pathol-\\nogy, Treatment, and Complications. Elaborately Illustrated\\nwith Colored Plates and other Illustrations. 2d Edition. In Press.\\nDULLES. What to Do First in Accidents and Poisoning.\\n5th Edition. New Illustrations. $1.00\\nFULLERTON. Surgical Nursing. 3d Edition. 69 Illus. $100\\nHAMILTON. Lectures on Tumors, from a Clinical Stand-\\npoint. Third Edition, Revised, with New Illustrations. 1 -^5\\nHEATH. Minor Surgery and Bandaging, nth Ed., Revised\\nand Enlarged. 176 Illustrations, Formulae, Diet List, etc. $1.25\\nHEATH. Injuries and Diseases of the Jaws. 4th Edition.\\n187 Illustrations. $4. 50\\nHEATH. Lectures on Certain Diseases of the Jaws. 64 Illus-\\ntrations. Boards, .50", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0331.jp2"}, "332": {"fulltext": "20 SUBJECT CATALOGUE.\\nHORWITZ. Compend of Surgery and Bandaging, including\\nMinor Surgery, Amputations, Fractures, Dislocations, Surgical Dis-\\neases, and the Latest Antiseptic Rules, etc., with Differential Diagno-\\nsis and Treatment. 5th Edition, very much Enlarged and Rear-\\nranged. 167 Illustrations, 98 Formulae. Clo., .80 Interleaved, $1.25\\nJACOBSON. Operations of Surgery. Over 200 Illustrations.\\nCloth, $3.00 Leather, $4.00\\nJACOBSON. Diseases of the Male Organs of Generation.\\n88 Illustrations. $6.00\\nLANE. Surgery of the Head and Neck, no Illustrations.\\n2d Edition. $5.00\\nMACREADY. A Treatise on Ruptures. 24 Full-page Litho-\\ngraphed Plates and Numerous Wood Engravings. Cloth, $6.00\\nMAYLARD. Surgery of the Alimentary Canal. 97 Illustrations.\\n2d Edition, Revised. Just Ready. #3.00\\nMOULLIN. Text-Book of Surgery. With Special Reference to\\nTreatment. 3d American Edition. Revised and edited by John B.\\nHamilton, m.d., ll.d., Professor of the Principles of Surgery and\\nClinical Surgery, Rush Medical College, Chicago. 623 Illustrations,\\nover 200 of which are original, and many of which are printed in\\ncolors. Handsome Cloth, $6.00; Leather, $7.00\\nROBERTS. Fractures of the Radius. A Clinical and Patho-\\nlogical Study. 33 Illustrations. $1.00\\nSMITH. Abdominal Surgery. Being a Systematic Description ot\\nall the Principal Operations. 224 Illus. 6th Ed. 2 Vols. Clo., $10.00\\nSWAIN. Surgical Emergencies. Fifth Edition. Cloth, $1.75\\nVOSWINKEL. Surgical Nursing. Second Edition, Revised and\\nEnlarged, in Illustrations. $1.00\\nWALSHAM. Manual of Practical Surgery. 7th Ed., Re-\\nvised and Enlarged. 483 Engravings, loco pages. Just Ready. $3.50\\nTHROAT AND NOSE (see also Ear).\\nCOHEN. The Throat and Voice. Illustrated. .40\\nHALL. Diseases of the Nose and Throat. Two Colored\\nPlates and 59 Illustrations. New Edition Preparing.\\nHOLLOPETER. Hay Fever. Its Successful Treatment. $1.00\\nKNIGHT. Diseases of the Throat. A Manual for Students.\\nIllustrated. Nearly Ready.\\nMACKENZIE. Pharmacopoeia of the London Hospital for\\nDis. of the Throat. 5th Ed., Revised by Dr. F. G. Harvey. $1.00\\nMcBRIDE. Diseases of the Throat, Nose, and Ear. A Clinical\\nManual. With colored Illus. from original drawings. 2d Ed. $6.00\\nPOTTER. Speech and its Defects. Considered Physiologically,\\nPathologically, and Remedially. $1.00\\nURINE AND URINARY ORGANS.\\nACTON. The Functions and Disorders of the Reproductive\\nOrgans in Childhood, Youth, Adult Age, and Advanced Life,\\nConsidered in their Physiological, Social, and Moral Relations.\\n8th Edition. $1.75", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0332.jp2"}, "333": {"fulltext": "MEDICAL BOOKS. 21\\nBEALE, One Hundred Urinary Deposits. On eight sheets,\\nfor the Hospital, Laboratory, or Surgery. Paper, $2.00\\nHOLLAND. The Urine, the Gastric Contents, the Common\\nPoisons, and the Milk. Memoranda, Chemical and Microscopi-\\ncal, for Laboratory Use. Illustrated and Interleaved. 6th Ed. $1.00\\nJACOBSON. Male Organs of Generation. 88 Illus. $6.00\\nKLEEN. Diabetes and Glycosuria. $2.50\\nMEMMINGER. Diagnosis by the Urine. 2d Ed. 24 Illus. $1.00\\nMORRIS. Renal Surgery, with Special Reference to Stone in the\\nKidney and Ureter and to the Surgical Treatment of Calculous\\nAnuria. Illustrated. $2.00.\\nMOULLIN. Enlargement of the Prostate. Its Treatment and\\nRadical Cure. 2d Edition. Illustrated. Just Ready. $*-7S\\nMOULLIN. Inflammation of the Bladder and Urinary Fever.\\nOctavo. $1-50\\nSCOTT. The Urine. Its Clinical and Microscopical Examination.\\n41 original Lithographic Plates and other Illustrations. Quarto.\\nCloth, $5.00\\nTYSON. Guide to Examination of the Urine. For the Use of\\nPhysicians and Students. With Colored Plate and Numerous Illus-\\ntrations engraved on wood. 9th Edition, Revised. $i-*5\\nVAN NUYS. Chemical Analysis of Urine. 39 Illus. $1.00\\nVENEREAL DISEASES.\\nCOOPER. Syphilis. 2d Edition, Enlarged and Illustrated with\\n20 full-page Plates. $5-\u00c2\u00b0o\\nGOWERS. Syphilis and the Nervous System. 1.00\\nSTURGIS. Student s Manual of Venereal Diseases. 7th\\nRevised and Enlarged Edition. i2mo. In Press.\\nVETERINARY.\\nBALLOU. Veterinary Anatomy and Physiology. 29 Graphic\\nIllustrations. .80; Interleaved, $1.25\\nTUSON. Veterinary Pharmacopoeia. Including the Outlines of\\nMateria Medica and Therapeutics. 5th Edition. $2.25\\nWOMEN, DISEASES OF.\\nBYFORD (H. T.). Manual of Gynecology. Second Edition,\\nRevised and Enlarged by 100 pages. 341 Illustrations. #300\\nDUHRSSEN. A Manual of Gynecological Practice. 105\\nIllustrations. 1 -S\u00c2\u00b0\\nFULLERTON. Surgical Nursing. 3d Edition, Revised and\\nEnlarged. 69 Illustrations. $1.00\\nLEWERS. Diseases of Women. 146 Illus. 5th Ed. $2.50\\nMONTGOMERY. A Text-Book of Practical Gynecology.\\nAbcut 500 Handsome Illustrations. 8vo. Nearly Ready.\\nWELLS. Compend of Gynecology. Illustrated. 2d Edition.\\n.80; Interleaved, $1. 25", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0333.jp2"}, "334": {"fulltext": "22 SUBJECT CATALOGUE.\\nCOMPENDS.\\nFrom The Southern Clinic.\\nWe know of no series of books issued by any house that so fully\\nmeets our approval as these ?Quiz-Compends?. They are well ar-\\nranged, full, and concise, and are really the best line of text-books that\\ncould be found for either student or practitioner.\\nBLAKISTON S ?QUIZ-COMPENDS?\\nThe Best Series of Manuals for the Use of Students.\\nPrice of each, Cloth, .80. Interleaved, for taking Notes, $1.25.\\n43f~ These Compends are based on the most popular text-books\\nand the lectures of prominent professors, and are kept constantly re-\\nvised, so that they may thoroughly represent the present state of the\\nsubjects upon which they treat.\\ng~ The authors have had large experience as Quiz-Masters and\\nattaches of colleges, and are well acquainted with the wants of students.\\nJ%$~ They are arranged in the most approved form, thorough and\\nconcise, containing over 6oo fine illustrations, inserted wherever they\\ncould be used to advantage.\\nJ g~ Can be used by students of any college.\\n4\u00c2\u00ae* They contain information nowhere else collected in such a\\ncondensed, practical shape. Illustrated Circular free.\\nNo. i. POTTER. HUMAN ANATOMY. Sixth Revised and\\nEnlarged Edition. Including Visceral Anatomy. Can be used\\nwith either Morris s or Gray s Anatomy. 117 Illustrations and 16\\nLithographic Plates of Nerves and Arteries, with Explanatory\\nTables, etc. By Samuel O. L. Potter, m.d., Professor of the\\nPractice of Medicine, College of Physicians and Surgeons, San\\nFrancisco Brgade Surgeon, U. S. Vol.\\nNo. 2. HUGHES. PRACTICE OF MEDICINE. Part I. Sixth\\nEdition, Enlarged and Improved. By Daniel E. Hughes, m.d.,\\nPhysician-in-Chief, Philadelphia Hospital, late Demonstrator ot\\nClinical Medicine, Jefferson Medical College, Phila.\\nNo. 3. HUGHES. PRACTICE OF MEDICINE. Part II.\\nSixth Edition, Revised and Improved. Same author as No. 2.\\nNo. 4. BRUBAKER. PHYSIOLOGY. Tenth Edition, with\\nIllustrations and a table of Physiological Constants. Enlarged\\nand Revised. By A. P. Brubaker, m.d., Professor of Physiology\\nand General Pathology in the Pennsylvania College of Dental\\nSurgery Adjunct Professor of Physiology, Jefferson Medical\\nCollege, Philadelphia, etc.\\nNo. 5. LANDIS. OBSTETRICS. Sixth Edition. By Henry G.\\nLandis, m.d. Revised and Edited by Wm. H. Wells, m.d.,\\nInstructor of Obstetrics, Jefferson Medical College, Philadelphia.\\nEnlarged. 47 Illustrations.\\nNo. 6. POTTER. MATERIA MEDICA, THERAPEUTICS,\\nAND PRESCRIPTION WRITING. Sixth Revised Edition\\n(U. S. P. 1890). By Samuel O. L. Potter, m.d., Professor of\\nPractice, College of Physicians and Surgeons, San Francisco;\\nBrigade Surgeon, U. S. Vol.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0334.jp2"}, "335": {"fulltext": "MEDICAL BOOKS. 23\\nPQUIZ-COMPENDS Continued.\\nNo. 7. WELLS. GYNECOLOGY. Second Edition. By W M H.\\nWells, m d., Instructor of Obstetrics, JeffersoD College, Philadel-\\nphia. 140 Illustrations.\\nNo. 8. GOULD AND PYLE. DISEASES OF THE EYE\\nAND REFRACTION. Second Edition. Including Treatment\\nand Surgery, and a Section on Local Therapeutics. By George\\nM. Gould, m.d., and W. L Pyle, m.d. With Formulae, Glossary,\\nTables, and 109 Illustrations, several of which are Colored.\\nNo. 9. HORWITZ. SURGERY, Minor Surgery, and Bandag-\\ning. Fifth Edition, Enlarged and Improved. By Orvillb\\nHorwitz, b. s., m.d., Clinical Professor of Genito- Urinary Surgery\\nand Venereal Diseases in Jefferson Medical College Surgeon to\\nPhiladelphia Hospital, etc. With 98 Formulae and 71 Illustrations.\\nNo. 10. LEFFMANN. MEDICAL CHEMISTRY. Fourth\\nEdition. Including Urinalysis, Animal Chemistry, Chemistry of\\nMilk, Blood, Tissues, the Secretions, etc. By Henry Lbffmann,\\nm.d., Professor of Chemistry in Pennsylvania College of Dental\\nSurgery and in the Woman s Medical College, Philadelphia.\\nNo. 11. STEWART. PHARMACY. Fifth Edition. Based upon\\nProf. Remington s Text-Book of Pharmacy. By F. E. Stewart,\\nm.d., ph.g., late Quiz-Master in Pharmacy and Chemistry, Phila-\\ndelphia College of Pharmacy; Lecturer at Jefferson Medical\\nCollege. Carefully revised in accordance with the new U. S. P.\\nNo. 12. BALLOU. VETERINARY ANATOMY AND PHY-\\nSIOLOGY. Illustrated. By Wm.R. Ballou, m.d., Professor\\nof Equine Anatomy at New York College of Veterinary Surgeons\\nPhysician to Bellevue Dispensary, etc. 29 graphic Illustrations.\\nNo. 13. WARREN. DENTAL PATHOLOGY AND DEN-\\nTAL MEDICINE. Third Edition, Illustrated. Containing\\na Section on Emergencies. By Geo. W. Warren, d.d.s., Chief\\nof Clinical Staff, Pennsylvania College of Dental Surgery.\\nNo. 14. HATFIELD. DISEASES OF CHILDREN. Second\\nEdition. Colored Plate. By Marcus P. Hatfield, Profes-\\nsor of Diseases of Children, Chicago Medical College.\\nNo. 15. KIRKBRIDE. GENERAL PATHOLOGY. Illustrated\\nby J homas S. Kirkbride, Director of the Laboratories, Fhila-\\nde phia Polyclinic; Assistant Pathologist, Philadelph a Hospital,\\netc. Preparing.\\nNo. 16. DISEASES OF THE SKIN. By Jay F. Schamberg,\\nm.d., Professor of Diseases of the Skin, Philadelphia Polyclinic.\\n2d Edition, Revised, ice handsome Illustrations.\\nPrice, each, Cloth, .80. Interleaved, for taking Notes, $1.25.\\nIn preparing, revising, and improving Blakiston s Quiz-Com-\\npends the particular wants of the student have always been kept in\\nmind.\\nCareful attention has been given to the construction of each sentence,\\nand while the books will be found to contain an immense amount of\\nknowledge in small space, they will likewise be found easy reading\\nthere is no stilted repetition of words the style is clear, lucid, and dis-\\ntinct. The arrangement of subjects is systematic and thorough there\\nIs a reason for every word. They contain over 600 illustrations.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0335.jp2"}, "336": {"fulltext": "Morris\\nAnatomy\\nSecond Edition, Revised and Enlarged.\\n790 Illustrations, of which many\\nare in Colors.\\nRoyal Octavo. Cloth, $6.00 Sheep, $7.00\\nHalf Russia, $8.00.\\nProm. The Medical Record, New York.\\nThe reproach that the English language can boast of no\\ntreatise on anatomy deserving to be ranked with the masterly\\nworks of Henle, Luschka, Hyrtl, and others, is fast losing\\nits force. During the past few years several works of great\\nmerit have appeared, and among these Morris s Anatomy\\nseems destined to take first place in disputing the palm in\\nanatomical fields with the German classics. The nomencla-\\nture, arrangement, and entire general character resemble\\nstrongly those of the above-mentioned handbooks, while in\\nthe beauty and profuseness of its illustrations it surpasses\\nthem. The ever-growing popularity of the book\\nwith teachers and students is an index of its value, and it\\nmay safely be recommended to all interested.\\nFrom The Philadelphia Medical Journal.\\nOf all the text-books of moderate size on human anatomy\\nin the English language, Morris is undoubtedly the most\\nup-to-date and accurate.\\nHand*, me Descriptive Circular, with Sample Pages and\\nColored Illustrations, will be sent free upon application.", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0336.jp2"}, "337": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0337.jp2"}, "338": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0338.jp2"}, "339": {"fulltext": "", "height": "3595", "width": "2228", "jp2-path": "refractionhowtor00thor_0339.jp2"}, "340": {"fulltext": "", "height": "3864", "width": "2508", "jp2-path": "refractionhowtor00thor_0340.jp2"}}