THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT OF Mrs. Clifford B. Walker TECHNIC OF REFRACTION Trial Case and Refractive Instruments A Manual of Practical Refraction with Instruc- tions for the Operation of the Trial Case and Refractive Instruments and Methods for Successfully Carrying Out a Case of Ocular Refraction By THOMAS G. ATKINSON, M. D. Author of Oculo-Refractioe Cyclopedia and Dictionary, Essentials of Refraction, Func- tional Diagnosis, etc. Editor, "The Eye, Ear, Nose and Throat Monthly." Contributor to Various Scientific Publications on Oculo- Refraction. Published by THE PROFESSIONAL PRESS, Inc. Chicago, 111. 1922 Copyright. 1922. Biomedical Library ww -306 FOREWORD. After all is said and done, the practical end of ocular refraction consists in its technique ; that is to say, in the most skillful and efficient application to the case in hand of the methods and apparatus at one's disposal, and the most intelligent evaluation of their findings. The proper manipulation of these instruments is, therefore, an ex- ceedingly important part of refraction; it is, in fact, the practice of refraction. The simplest method, or instru- ment. is susceptible of all degrees of value and efficiency, according to the skill and accuracy with which it is ap- plied. The instructions given in this little book are those which the design of the various instruments and the concensus of the best experience have shown to be the most effective way of getting all that is to be got out of the procedure in question. Each technique is set out, in tabulated, consecu- tive form, step by step, so that the student or practitioner may, by its aid, perform the operation from start to finish without any uncertainty or hesitation. The book is, in short, a working manual of practical refraction. If the reader has never yet performed the task of refracting, he may here learn, at first hand, precisely how to proceed. If he has been using the methods and instruments here described by different technics, he will find his work greatly simplified and its efficiency increased by following the procedures laid down in these pages. THE AUTHOR. CONTENTS CHAPTER I The Trial Case Stenopaic Slit Junes' Method of Ste- nopaic Slit Chromatic or Cobalt Test Prisms Con- vergence Tests The Maddox Rod Cross Cylinder Test Visual Acuity Test 7 CHAPTER II The Retinoscope Static Retinoscopy Finding the Chief Meridians Dynamic Retinoscopy Cross' Method Sheard's Method The Genothalmic Retinoscope The Geneva Ophthalmoscope Retinoscope Thorington Ax- onometer 23 CHAPTER III The Ophthalmoscope Direct Method Indirect Method The Geneva Ophthalmoscope and Retinoscope 30 CHAPTER IV The Ophthalmometer Universal Ophthalmometer C-I Ophthalmometer Meyrowitz-Javal Ophthalmometer 4'2 CHAPTER V The Phoroptometer The DeZeng Phoroptometer or Phoroptcr The Ski-Optometer The Genothalmic Re- fractor Binocular Muscle Tests Monocular Muscle Tests Duction Tests Muscle Exercises 50 CHAPTER VI The Perimeter Standard Registering Perimeter Stereo- Campimeter with Lloyd's Slate 6'.) CHAPTER VII Tests for Color Blindness Holmgren's Wool Test Jen- ning's Self-Recording Test Williams Lantern Test Nagel's Test 73 CHAPTER VIII Miscellaneous The Punctumeter The Ametropometer The Dynamic Refractor The Placidoscope Interpupil- lary Gauge 77 CHAPTER IX The Complete Examination and Record Vision and Visual Acuity Subjective Tests Objective Tests Muscle Tests The Near Point Correction and Con- firmation The Ophthalmoscope The Visual Field 8."> CHAlTliR 1. THE TRIAL CASE. The original and essential contents of the trial case con- sist of sets of graded ophthalmic lenses, plus and minus, spherical and cylindrical, representing various dioptric intervals, according to the numerical completeness of the case ; a set of prisms graded in prism degrees or dioptres ; and a trial frame, equipped with a graduated arc-rim for placing the axis of a cylinder, in which to mount the lenses and prisms before the patient's eyes. The working value of these lenses and prisms depends upon knowing how to apply them to the detection and measurement and correction of refractive errors. There are several systems of technic for this working applica- tion of lenses and prisms. In addition to lenses and prisms, however, every well- equipped modern trial case contains certain other devices for the more rapid and accurate performance of ocular refraction, which have come to be recognized as standard integral parts of the trial case. Chief among these are the Maddox rod, the stenopaic slit, and the cobalt or chromatic glass. The following instructions cover the commonly-accepted, standard methods of employing these contents of the trial case for testing refraction and muscle balance. Fogging. i. With the chart at 20 feet, place before the eye to be tested [the other eye being meantime excluded from 8 TECHNIC OF REFRACTION vision] a plus lens strong enough to blot out both test type letters and astigmatic wheel. 2. Direct patient's attention to the astigmatic chart. Gradually reduce the plus power before the eye by put- ting in front of it successively stronger minus spheres, beginning with minus .50 D. and increasing .50 D at a time until patient can just discern the astigmatic wheel. 3. If all the spokes of the wheel are seen with equal clearness, there is no astigmatism. 4. If one of the spokes stands out more clearly than all the rest, there is astigmatism. Correct it at once by finding the weakest minus cylinder which, with its axis at right angles to the clearest spoke, makes them all equally clear. 5. Leaving the cylinder (if any) in place, continue to reduce the plus spherical power by increasing the strength of the minus sphere -5oD. or even .25 D. at a time, until patient can read 20/20 type. 6. The net amount of lens power now before the eye, including the cylinder [if any], is the patient's distance correction. 7. If there is no astigmatism, as shown by section 3, then, of course, item 4 will be omitted. 8. Example : A plus 5 D. sphere completely fogs vision. With a minus i D. sphere before the plus 5 D. patient can just begin to see the astigmatic wheel. The spoke at 90 deg. stands out clearest. A minus .75 cylinder, axis 180, makes all clear alike. By increasing the minus sphere to 2 D. patient reads 20/20. Correction : minus ,75 D. cylin- TRIAL CASE AND REFRACTIVE INSTRUMENTS 9 der, axis 90, with a plus 3 D. sphere i.e. the difference between the plus 5 fogging lens and the minus 2 reduc- ing lens. Stenopaic Slit. 1. Place the slit before the eye to be tested, the other eye being meanwhile shut off by means of a blank. 2. Slowly revolve the slit before the eye, directing the patient's attention to the test chart, until best possible vision is obtained, and note the angle at which the slit stands. 3. If vision at this point is 20/20, this meridian of the eye is normal. If not, try a weak plus sphere in front of the slit. If this improves the vision, find the plus sphere which makes vision 20/20. If plus spheres make vision worse, change to minus, and find the minus sphere which makes vision 20/20. The sphere, plus or minus, which makes vision 20/20 is the measure of the refractive error in this meridian of the eye. 10 TECHNIC OF REFRACTION 4. Now turn the slit 90 degrees, to the meridian of worst vision, and repeat the process described in section 3. 5. You now have the angles of best and worst vision, and the refractive error [if any] of each. Prescribe a cylinder equal to the difference between the two meridians, with its axis at right angles to the worse meridian, and a sphere equal to the error in the best meridian. 6. Example : Vision is best with slit at 90 deg. A plus 2 sphere makes it 20/20. Vision is worst at 180 deg. A plus 3.50 makes it 20/20. Correction: A plus 1.50 cylin- der, axis 90 deg., combined with a plus 2 sphere. Example : Vision is best with slit at 30 deg. A plus 2 sphere makes it 20/20. Vision is worst at 120 deg. and a minus 3 makes it 20/20. In this case the worst meridian is minus, hence the correction is: A minus 5 cylinder [algebraic difference between the two meridians], axis 30 deg., with a plus 2 sphere. Junes' Method of Using the Stenopaic Slit. 1. Seat the patient 20 feet from a clock dial chart. Examine one eye at a time, excluding the other eye from vision. 2. If, with the naked eye, the patient sees all the lines of the dial equally black, there is no astigmatism. His error, if he has any, is spherical. 3. Place the slit before the eye, set at any angle at ran- dom. If he continues to see all lines equally black, the eye is either emmetropic or hyperopic. Place a weak plus sphere before the slit. If he now sees one line blacker TRIAL CASE AND REFRACTIVE INSTRUMENTS 11 than the rest [phenomenon of the black line] he is emme- tropic. If he still continues to see all lines alike, he is hyperopic. Continue to place more and more plus sphere before the slit until the phenomenon of the black line appears; the spherical power immediately preceding this is the measure of his hyperopia. 4. If on placing the slit before the eye the phenomenon of the black line immediately appears, the eye is myopic. Place successively stronger concave lenses before the slit until the phenomenon of the black line disappears and all look black alike. The weakest minus lens which accom- plishes this is the measure of his myopia. 5. If, with the naked eye, the patient sees the phenome- non of the black line, the eye is astigmatic, and the direc- tion of the clearest line is one of the principal meridians. 6. Place the slit before the eye with the axis of the slit coinciding with the blackest line. If the phenomenon of the black line disappears, the eye is either emmetropic or hyperopic. Place a weak plus sphere before the slit. If the phenomenon of the black line re-appears, the eye is emmetropic. If not, it is hyperopic. Place successively stronger plus spheres before the slit until the phenomenon re-appears. The spherical power immediately preceding this is the measure of the hyperopia of that meridian. 7. If, on placing the slit before the eye with its axis along the blackest line, the phenomenon of the black line persists, this meridian of the eye is myopic. The weakest concave lens which causes the phenomenon to disappear is the measure of its myopia. 12 TECH^IC OF REFRACTION 8. Now rotate the slit to the opposite angle, at right angles to the first position, and repeat the test. In this way the refraction of the two principal meridians is ob- tained, and the correction calculated in the usual way. 9. If, with the naked eye, the patient cannot distin- guish any of the lines on the dial, the eye is either very myopic or else there is hyperopia complicated with astig- matism. 10. Place a weak minus lens before the eye, without any slit. If all the lines of the chart become equally dis- tinct, the eye is myopic only. Place the slit before the eye at any angle, and proceed as in section 4 to measure to myopia. 11. If, with the concave lens, the phenomenon of the black line appears, there is compound myopic astigma- tism. Place the slit before the eye, with its axis coincid- ing with the blackest line, and proceed to measure the two principal meridians as instructed in Sections 7 and 8. 12. If a concave lens does not improve the vision, place before the naked eye a convex lens sufficiently strong to give vision of the dial. If all the lines of the chart now become equally clear, the eye is highly hyperopic only. Place the slit before the eye at any angle, and proceed as instructed in Section 3 to measure his hyperopia. 13. If, with the convex lens, the phenomenon of the black line appears, there is compound hyperopic astig- matism. Place the slit before the eye, with its axis coin- ciding with the blackest line, and proceed to measure the two principal meridians as instructed in Sections 6 and 8. TRIAL CASE AND REFRACTIVE INSTRUMENTS 13 14. If, in the carrying out of the tests in any of the cases of astigmatism, one meridian exhibits the signs of hyperopia and the other of myopia, the astigmatism is, of course, mixed. Each meridian is to be measured accord- ing to its kind of error. Chromatic or Cobalt Test. 1. With the cobalt lens before the eye to be tested, [the other eye being excluded from vision], the patient's at- tention is directed to a small circular light, usually at 20 feet. 2. If patient is hyperopic, he sees a violet centre with a ring of red around it. Plus correction is added until he sees no more red around the centre, or until there is a slight blue ring. 3. If patient is myopic, he sees a red center with a blue ring around it. Minus spherical correction is added until he sees no blue ring, or until it is very faint. 4. If patient has hyperopic astigmatism, he sees red on each side of the blue, corresponding to the chief meridians 14 TECHNIC OF REFRACTION of the astigmatism. Add plus correction until the red on each side almost disappears, then minus cylinders, axis where the red shows, until the red appears at right angles to the axis of the cylinder, i.e. until a red ring appears around the center. Now add plus spherical power until there is no longer a red ring, but a thin blue ring. 5. If patient has myopic astigmatism, he sees blue on each side corresponding to the chief meridians. Put on minus cylinders until there is a red ring around the center ; then add plus spherical lenses until there is no red ring, but a narrow blue ring. 6. If patient has mixed astigmatism, he sees blue up and down and red on each side, or vice versa. Put on plus spheres until there is a little red left in its place; then minus cylinders, axis where the red is, until there is a red ring around the center. After that, add plus spher- ical power until there .is no more red ring, but a thin blue ring. Prisms. Prisms are used for three distinct purposes : [ i ] To test the functional strength or efficiency of the extrinsic mus- TRIAL CASE AND REFRACTIVE INSTRUMENTS 15 cles, [2] To exercise defective muscles, [3] To test con- vergence. Duction. 1. Seat the patient 20 feet from a small white circle of light, with his eyes on the same horizontal plane with the light. Instruct him to look steadily at the light. 2. To test the duction of the internal recti muscles, be- gin with a small strength prism, base in, and gradually add more and more prism power,' base in, until the patient can no longer maintain single vision of the light. N. B. It is advisable to add this prism power equally to both eyes, as far as possible, and to proceed by as small stages of increase as practicable. A normal pair of eyes should be able to overcome about 30 prism dioptres, divided between the two eyes. 3. To test the duction of the externals, proceed in the same fashion, but with the prisms placed base out. A normal pair of eyes should overcome about 8 to 10 prism dioptres. 4. To test the vertical muscles, the same procedure is called for, with the base of the prism down to test the superior recti, base up to test the inferior. Normal ver- tical muscles should overcome 4 to 6 prism dioptres. Muscle Exercises. To exercise the ocular muscles, the same procedure is required as in testing their duction, but the exercises must be cautiously graded, increasing the power of the prisms gradually, over several sittings, until the patient is able 16 TECHNIC OF REFRACTION to overcome his normal amount. Put, always, the apex of the prism over the muscle to be exercised, and divide the prism power between the two eyes, unless, of course, it is desired to exercise one eye specially. N. B. Rotary prisms are much preferable for duction and muscle exercises, as they permit of continuously graded increase of prism power. Convergence Tests. There are numerous varieties of this test, differing principally in the nature of the chart employed, such as the dot and line, the line of type recommended by Sheard, and others. They are all essentially the same, however, in principle and general technique, and we shall here de- scribe the test in connection with the graded line and index pointer. The chart consists of a horizontal black line, from the middle of which rises a black index pointer, about a centimeter in height. On either side of the pointer the line is graded into centimeters. 1. With the chart held 25 cm. from the patient's eyes [or at whatever distance the test is to be made] place be- fore one eye a 6 dioptre prism, base up. This will make the black line appear double, the false line, seen by the prismed eye, being below the true one. 2. If the index pointer of the lower line stands ex- actly under the pointer of the upper line, there is no im- balance. 3. If the index pointer stands to one side of the pointer of the upper line, toward the same side as the prismed TRIAL CASE AND REFRACTIVE INSTRUMENTS 17 eye, there is esophoria. Note the number of centimeters on the upper line scale to which the lower pointer points. Divide this number by the distance in meters at which the test is made, to find the prism dioptres of esophoria. Thus, if the lower pointer is shifted so as to stand at i cm., then i divided by .25 equals 4 prism dioptres of esophoria. 4. If the lower index pointer is shifted to the opposite side from that of the prismed eye, there is exophoria, to be measured in the same way as the esophoria in the pre- vious paragraph. N. B. It is best to make a practice of always plac- ing the displacing prism before the same eye say the right eye so that esophoria will always be shown by the lower pointer shifting to the right, and exophoria by its shifting to the left. 5. To test the vertical muscles, turn the chart so that the black line is vertical, and place before the right eye a 12 or 15 dioptre prism, base in, which will double the line laterally. 6. If the two index pointers are level with each other, there is no imbalance. If the pointer of the false line is shifted up or down, vertical imbalance is indicated, hyper- phoria of right or left eye, as the case may be, and the amount is found, as before, by dividing the distance [in meters] into the centimeter scale at which the shifted pointer stands. 18 TECHNIC OF REFRACTION The Maddox Rod. The purpose of this is to dissociate the retinal images, so that the extrinsic muscles of the eyes will assume their position of rest, and thus disclose any imbalance which may exist. Its use is limited to tests at infinity. 1. Seat the patient twenty feet from the object, which should be a small circle of white light. 2. For testing the lateral muscles, place the Maddox rod before one eye and either leave the other uncovered or place before it a plane red glass the latter is better, so as to make the images further dissimilar. Turn the rod with its axis at 180 degrees ; this will draw out the light into a vertical streak, while the other eye sees a red circle of light. 3. If the two images the white streak and the red cir- cle of light are separated in the same direction as the eyes viewing them, there is esophoria. The weakest prism, with its base out, which will bring the two images together, is the measure of the esophoria. TRIAL CASE AND REFRACTIVE INSTRUMENTS 1!) 4. If the two images are separated in the opposite di- rection from the eyes viewing them i.e., with the rod be- fore the right eye, the white streak is seen to the left side ["crossed"] there is exophoria. The weakest prism, with its base in, which brings the images together is the measure of the exophoria. 5. For testing the vertical muscles, set the rod at 90 deg., which presents a horizontal streak of white light. 6. If the two images are separated, one above the other, there is vertical imbalance. The weakest prism, placed base up before the eye whose image is underneath, or base clown before the eye whose image is above, which brings the two images together on the same horizontal plane, is the measure of the error. 7. Place two Maddox rods, one before each eye, both set either at 90 or at 180 degrees. If the white streak does not appear to the patient to be horizontal or vertical, respectively, but oblique, there is cyclophoria, which may be measured by turning the rod in the trial-frame until the streak appears vertical or horizontal, as the case may be. The number of degrees that the rod then stands from 90 or 180 is the measure of the cyclophoria. Cross-Cylinder Test. i. Having determined the patient's near point by the ordinary methods, and [in the case of presbyopia] prop- erly corrected, substitute for the type chart a T chart, and place before the eye a compound lens equivalent to a cross-cylinder, say a plus .50 sphere and a minus I cylin- der, axis 90, thus creating a false astigmatism of .50 D, 20 TECHNIC OF REFRACTION hyperopic in one meridian and .50 D. myopic in the other. 2. If, before applying this test, the eyes were in exact focus for near point, there will be no perceptible differ- ence in the two arms of the T. 3. If one arm of the T is blacker than the other, then the eyes were not in exact focus. Add plus spherical power until the two arms are equally black. This repre- sents the patient's true correction for near point. Ives Screen. 1. Turn the gratings so that the bands or squares are too small to be visible to the patient. 2. Rotate the gratings very slowly by means of the milled head until patient is just able to discern the pat- tern. Read the acuity direct from the scale. TRIAL CASE AND REFRACTIVE INSTRUMENTS 21 3. Ask the patient in what direction the lines lie. Change this direction between tests so that patient will not know which way to expect them to appear. 4. For subjective test reduce the lines or squares from easy visibility to just visibility ; for objective test, increase them from non-visibility to just visibility. In the first in- stance, accommodation is an active factor, in the latter the accommodation is at rest. 5. To locate the axis of astigmatism, use the lines. Set the gratings so that the lines are barely visible. 6. Rotate until the lines are orientated together in their holder so that the bands appear clearest. Read the angle from the degree scale on back of front plate. /. To verify the result, reduce still more the width of the lines, and when the minimum width of line visible 22 TECHNIC OF REFRACTION to the patient is reached, orient the entire screen to right or left, and the lines will disappear. 8. When using the squares, the brightness of the light remains constant. But when using the lines, move the lamp toward or away from the gratings, by means of the sliding sleeve, so as to vary the intensity of illumination in a manner to keep the field uniformly illuminated. TRIAL CASE AND REFRACTIVE INSTRUMENTS 23 CHAPTER II. THE RETINOSCOPE. The retinoscope furnishes the only available objective method of determining the refraction of the eye, by means of shadow phenomena produced, observed, and modified by means of the instrument. Considerable practice is needed to be able to execute the manoeuvers necessary to obtain a good "reflex," and to observe the shadows; and not until this has become easy can the operator devote the requisite attention to interpreting the shadows. To attain this proficiency it is advisable to practice with a schematic eye. It is assumed in the^e instructions that the operator is familiar with this elementary phase of retinoscopy. In the technique here described it is further assumed that the operator is using a plane mirror. Some retino- scopes are made with a concave mirror, the advantages of which are a more intense light and the usefulness of such a mirror for ophthalmoscopy. If a concave mirror 24 TECH NIC OF REFRACTION is used, two points must be observed : [ i ] The operator must take care that he works at such a distance from the patient as to be outside the focal length of the mirror; [2] The movements of the shadow will be precisely the opposite of those seen with the plane mirror. Many beginners with the retinoscope make the mistake of watching the disc of light [made by the mirror] as it passes to and fro across the patient's face, instead of watching the shadows in the pupil, thus failing to get proper results. The light will, of course, always move in the same direction that the mirror is being moved, and has nothing to do with the case. It is the shadows that must be observed. There are two methods in retinoscopy, the static and dynamic. The former is employed with the patient's ac- commodation at rest; the latter with the accommodation in force. So far as the technical aspects of these two methods is concerned, the difference lies in the fact that in static retinoscopy we employ a neutralizing or "work- ing equivalent" lens, to equalize the distance at which we work, while in the dynamic method no equalizing or work- ing lens is used. Static Retinoscopy. i. The examination should be made in a darkened room not necessarily pitch dark, but sufficiently dark- ened that the patient's pupil when illuminated by the mirror shall stand out conspicuously in contrast to the surrounding darkness, on the same principle that the body of a theater is darkened to show up the illuminated stage. TRIAL CASE AND REFRACTIVE INSTRUMENTS 25 2.. If a non-illuminating retinoscope is used, the source of light should be placed just back of the patient's head, slightly to one side, on a level with the top of the ear. The best form of light is an incandescent electric lamp, of 50 candle power, enclosed in an opaque chimney, with an adjustable diaphragm through which the light may emerge. At the outset of the examination the diaphragm should be about 10 mm. in diameter; as neutralization is ap- proached, it should be reduced to half that diameter. 3. Seat the patient comfortably in a chair, either with his head against a head-rest or leaning slightly forward, and instruct him to look straight in front of him into in- finity. For this purpose it is better not to have the room perfectly dark, or the patient will be tempted to fix his eyes on the mirror of the retinoscope. If the room be merely darkened, he can fix upon some object at 20 feet, e.g., the distance test chart. For children a moving object [e.g., a revolving wheel] at 20 feet distance is an excel- lent "fixer." 4. Adjust your own stool so that your eyes are on the same horizontal plane with those of the patient. The dis- tance from the patient at which you work is immaterial, except for purposes of convenience and clear vision of the shadows. Fifty centimeters is a very convenient work- ing distance. The important point is to determine the distance accurately. This is perhaps best done by means of a tape measure attached to a movable bar or stand which can be placed in a vertical plane with the patient's forehead. 5. Place in the trial frame before the patient's eye a 20 TECHNIC OF REFRACTION plus lens whose focal length is equal to the distance at which you are working. This lens, known as the "work- ing equivalent" or "equalizing lens," is to be regarded as part of the patient's eye, and not to figure in any of the calculations of his error. 6. Throwing the light from the mirror into the patient's pupil, as nearly as possible along the visual axis, rotate it slightly, and not too fast, in the horizontal meridian. Too wide and too rapid excursions of the mirror defeat one's purpose, making it impossible to observe the shadows. 7. If no shadows are seen to move across the patient's pupils, the refraction is normal in that meridian. 8. If a shadow is seen to move across the pupil, one from each side, in the same direction that the mirror is being rotated, ["with the mirror"], the eye is hyperopic in that meridian. If the edges of the shadows are cres- centic and vertical, the error is probably a spherical one ; if the edges are straight and vertical, it is probably an astigmatism with its chief meridians "right," i.e., vertical and horizontal. In either case, proceed to correct that meridian. If, however, the edges of the shadows are in- clined or tipped, then change the movement of the mirror so as to rotate it at right angles to the edges of the shad- ows. 9. With the shadows moving "with the mirror," put a plus lens in the trial frame before the eye, beginning with low power, and add to it until no shadows can be seen moving across the pupil. The "point of reversal" has now been reached, and the shadows "neutralized." To make sure, add a little more plus lens, and observe that TRIAL CASE AND REFRACTIVE INSTRUMENTS 27 the movement of the shadows changes to the opposite di- rection. The lens power which just succeeded in abolish- ing the shadows is the measure and the correction of the error in this meridian. N. B. Two other indications are to be watched for at this point. First, when the point of neutralization is reached the appearance of the pupillary reflex will change from a dull red to a bright orange. Second, if the eye is astigmatic, as the point of reversal is approached a band or streamer of light will be seen lying across the corrected meridian, due to the fact that one meridian is corrected while the opposite one is still out of focus. 10. If, upon first beginning to rotate tne mirror, shad- ows are seen moving across the pupil in the opposite direc- tion to that in which the mirror is being rotated, the eve is myopic in that meridian and minus lens power must be used to neutralize them. All the other stipulations of sec- tions 8 and 9 apply equally to such a case. 11. Having satisfactorily neutralized the meridian un- der examination, make a notation of the angle of the meridian and the kind and amount of lens power needed to neutralize it. 12. With the correction left in the trial frame, now rotate the mirror in a direction exactly at right angles to its former rotation, thus "shadowing"' the opposite chief meridian. If no shadows are seen to move across the pupil in this direction, this meridian is also corrected, and the error is a spherical one simple hyperopia or myopia, as the case may be. 28 TECHNIC OF REFRACTION 13. If shadows are seen moving in this meridian "with the mirror," this meridian is still hyperopic. The case is one of astigmatism. Place a weak plus cylinder in the trial frame, with its axis at the opposite meridian to the one you are shadowing, and increase this cylinder until the shadow in this meridian is abolished. The power of this cylinder, added to the power of the sphere already before the eye, is the measure of the error in this meridian. The sphere and the cylinder, as they stand in the trial frame, is the correction of the total error. 14. If, on beginning to shadow the second meridian, shadows are seen moving "against the mirror," this merid- ian is still myopic, and minus cylinder lens power must be used to neutralize it, in the way described in section 13. The net sum of this cylinder and the sphere already before the eye, excluding the neutralizing or working lens, is the measure of the error in this meridian, and the sphere and cylinder, as they now stand in the trial frame, constitute the total correction. 15. If, on first beginning to shadow the eye, the shad- ows are seen to move inconsistently, with the mirror in some meridians and against it in others, and the pupillary area a mixture of light and shadow, there is probably an irregular astigmatism. In such a case find the best posi- tion of observation, and pick out the meridians which present the clearest shadows. 16. If the shadows, instead of moving regularly from side to side of the eye, with or against the mirror, seem to divide into two, which move toward each other, ["scis- sors movement"], it signifies one of three things, [i] ir- TRIAL CASE AND REFRACTIVE INSTRUMENTS 29 regular astigmatism, [2] tilted crystalline lens, or [3] lack of alignment of the refracting media of the eye. In such cases be sure to refract along the line of vision ; watch carefully for the division line, and refract that por- tion of the eye in which the reflex contains the visual line. Finding the Chief Meridians. In some cases the two chief meridians of the astig- matic eye reveal themselves under retinoscopy by the straight edges of the shadows and the angle at which these edges lie, as described in Section 8. In other cases these indications are not clear, and the operator must go on shadowing the horizontal meridian until, as neutraliza- tion is approached, the astigmatic band appears and indi- cates the lay of the chief meridians. To render this band as clear as possible, as soon as the meridian you are shadowing becomes neutralized, push the lamp away from your mirror, or draw it toward it, until the astigmatic band stands out distinctly, and the axis of the astigmatism will be revealed. This manoeuvre is, of course, not practicable with a self -illuminating retinoscope. Dynamic Retinoscopy. Use the same kind of retinoscope as for the static test, except that it should have a row of letters attached to the top of the mirror for the patient to fix with his vision. The position of the patient and operator are the same as in static retinoscopy. No neutralizing or working lens is 30 TECHNIC OF REFRACTION used in this test. As this is a binocular test, in which convergence is to play a part, both eyes should be left uncovered. Cross' Method. 1. Seating yourself at any convenient distance say 50 cm. from the patient, instruct him to read aloud the let- ters on the top of the mirror. According to Cross, he will exercise only that amount of accommodation which corresponds to the 3 I ratio between convergence and accommodation. 2. Rotating the mirror, as in the static technique, if there is no shadow, the refraction of the eye is normal, convergence and accommodation being in mathematical harmony, and the retina being conjugate with the mirror. 3. If the shadow is seen to move with the mirror, pa- tient is hyperopic. Add plus lens power before the eye until the shadow is abolished. If this neutralizing lens power is the same, or substantially the same, as arrived at by the static test, it represents the measure and cor- rection of the total error. If it is noticeably more than in the static test, the difference between them represents latent hyperopia, in the form of ciliary spasm. 4. If the shadow is seen to move against the mirror, patient is myopic. Ordinarily in such cases the test may be abandoned, since dynamic skiascopy, by Cross' method, has no special value in myopia. If you decide to continue it, however, put on a strong enough minus lens to make the shadow move with the mirror, and then proceed as though the eye were hyperopic, taking care to subtract the amount of the minus lens from the final result. TRIAL CASE AND REFRACTIVE INSTRUMENTS .'51 5. If latent hyperopia, or ciliary spasm, is shown to be present, correct all or as much of it as your judgment dictates, in addition to the manifest error, as shown by the static test. 6. In carrying out this method, the same indications of astigmatism must be watched for, and the same steps taken to determine and correct the two chief meridians, as set forth in describing the static test [see above] . Sheard's Method, According to Sheard, the only real value of dynamic skiascopy is to determine the patient's true near point, i.e., the near point where convergence and accommoda- tion coincide. For this purpose he has formulated the following method of procedure : 1. First determine the patient's distance error, and let him wear his distance correction during the dynamic test. 2. Push the fixation chart in advance of the retinoscope, say two or three inches, and while he reads the letters shadow the eye. 3. If the movement of the shadow is with the mirror, push the chart further forward until the movement be- comes against, and come forward with the mirror until it changes again to "with." 4. Repeat this manoeuvre until, with the chart some dis- tance in front of the mirror, you locate the nearest point of neutralization. This point is the patient's true near point, upon which his reading correction is to be calcu- lated. 32 TECHNIC OF REFRACTION The Genothalmic Retinoscope. This is a special form of self -illuminating retinoscope for performing retinoscopy. 1. First unscrew the upper part of the head from the lower part and see that the lamp is securely screwed into place. Then reassemble the base and the head, and se- curely lock them together. 2. Place the head on the battery handle, hitting the dent in the base of the head into the milled slot in the battery handle stem, and lock by turning a quarter of a turn to right or left. 3. Turn on the current by revolving to the right the nickeled ring No. 2 on the head of the battery handle. 4. Hold the mirror 40 inches from a screen, and move the ferrule tube on the stem up or down, until the area of light is nearest to a circular form and about the size of a dollar. This is the average place to use the light, but if more intensity is required, it may be obtained by mak- ing the light-area smaller. 5. Now apply the instrument to your face so that it rests securely against the nose and eyebrow with the sight- hole directly in front of your pupil, but with the mirror side away from the eye, and proceed to use it. The Geneva Ophthalmoscope and Retinoscope. To use the instrument as a Retinoscope : i. Turn the ophthalmoscope lens down against the bot- tom of the tube, and see that zero appears on dials Nos. 18 and 22, and the letters RET on dial No. 16. TRIAL CASE AND REFRACTIVE INSTRUMENTS 33 2. Seat patient facing away from window or strong light, and place instrument so that patient can see, with either eye, a test chart placed preferably 20 feet away. Any ordinary test chart will do. It steadies the patient's fixation and relaxes his accommodation. 3. Have patient place his chin in the chin-rest and his forehead in head-rest, with face squarely fitted to the frame. Direct him to look at the test-chart. 4. Run the instrument up toward patient as far as it will go, using handles No. 9 for that purpose. Place in lens clip No. 25 a plus lens of. such power as to fog pa- tient's vision to about the 80 line on chart ; ask him to read as many letters as he can on this and the following line. This relaxes accommodation very thoroughly. 5. See that the center of the end of the tube is in line with center of patient's pupil. 6. Look through peep-hole, and the reflex from pa- tient's pupil will be seen at other end of tube, as a round, red-illuminated area. 7. If reflex, instead of being orange-red, is a silvery white, the patient is looking at too great an angle from the line of the instrument, and the chart must be moved so 34 TECHNIC OF REFRACTION that the line of vision will be closer to the axis of the in- strument. If the reflex is a dirty grayish- white, patient is accommodating, and more fogging [plus] lens must be used. 8. When the proper color of reflex is obtained [orange red] tilt the mirror back and forth slowly, by means of handle No. 35, and note the movements of the shadow in the patient's pupil. 9. The mechanism permits of the mirror being tilted to and fro across any meridian of the eye. Use the mir- ror precisely as you would the hand retinoscope, [see Instructions for Static Retinoscopy], rotating into place any desired correcting lens, or combination of lenses, by means of dial wheels Nos. 16 and 18. Thorington Axonometer. A device to aid in finding the exact axis subtended by the band of light in retinoscopy. i. Place the disc in the trial frame so that the cornea of the examined eye coincides with the central opening in the disc. TRIAL CASE AND REFRACTIVE INSTRUMENTS 35 2. When the first meridian of astigmatism has been found and corrected, so that the astigmatic band appears, slowly turn the axonometer until the two heavy white lines appear to make a continuous line with the band of light. 3. The degree on the scale to which the arrow points is the axis for the correcting cylinder. 80 TECHNIC OF REFRACTION CHAPTER III. THE OPHTHALMOSCOPE. The ophthalmoscope is not, properly speaking, a re- fractive instrument. It was never intended to be used for detecting or measuring errors of refraction, but was de- signed for examining the fundus of the eye for pathologic appearances. It can be utilized for determining, in a rough qualitative fashion, refractive errors, and instruc- tions are here given for this purpose. The extreme dif- ficulty of the technic, however, and the numerous sources TRIAL CASE AND REFRACTIVE INSTRUMENTS 3? of error, make it a very inferior procedure to others at the refractionist's disposal. Examination of the fundus with the ophthalmoscope should take place in a darkened room not necessarily pitch dark, but sufficiently darkened to induce relaxation and to make the illuminated area of the eye stand out in contrast to the rest of the room. Where the ophthalmoscope is not a self-illuminating one, the source of light preferably a 50 C. P. incandes- cent lamp enclosed in an opaque chimney with a diaphragm should be placed to one side of the patient on the side of the eye to be examined, and on a level with the eye. It must be placed so that its light may fall, without inter- ference, upon the mirror of the ophthalmoscope, when this is being held very close to the patient's eye. As this is rather an awkward thing to do, a self-illuminating ophthalmoscope is greatly to be preferred. Direct Method. 1. Patient and operator should be seated, facing each other, so that their eyes are in the same horizontal plane. Operator must wear his correction, if he needs any. Pa- tient's accommodation must be thoroughly relaxed by fix- ing at infinity. This relaxation must be maintained throughout the examination. 2. Throw the reflected light from the mirror into the patient's pupil ; then gradually approach nearer and nearer to the patient's eye, until the mirror [with your eye at the peep-hole] is quite close to his eye. 38 TECHNIC OF REFRACTION 3. Relax your own accommodation. This is the most difficult part of the procedure for the novice. It can best be done by imagining that the fundus you are examining is away at the back of the patient's head. 4. If the details of the fundus do not at once come into view, wait a few moments. Your accommodation may be at fault, and may adjust itself in a few seconds. If you still do not get a view of the vessels and nerve-head, wheel a plus lens into the peep-hole and try again; if this improves your view, keep on wheeling stronger and stronger plus lenses into the peep-hole until you see the fundus. If a plus lens makes things worse, try minus lenses. 5. The plus or minus sphere which gives a clear view of the details of the fundus both operator's and patient's accommodation being relaxed is the measure of the pa- tient's spherical error. 6. If the patient is astigmatic, you will not be able to see the details of the fundus in all directions with the same spherical lens at the peep-hole of the mirror. One power will give a view of the eye-ground in one meridian, and a different power in the opposite meridian. These two lens-powers are the measures, respectively, of the error in the two meridians. 7. To examine the fundus for pathological appear- ances, use the same technique as given above ; in that case, however, it is not necessary to have your accommodation relaxed, or your own error corrected. Use any accom- modation or lens that will give a clear view of the eye- ground. TRIAL CASE AND REFRACTIVE INSTRUMENTS 39 Indirect Method. 1. Patient and operator sit facing each other, about an arm's length distant, with their eyes on the same horizontal plane. Operator must wear his correction. Patient's ac- commodation must be relaxed throughout the examination. 2. With your left hand hold a strong plus spherical lens, from 12 D. to 16 D., immediately in front of the patient's eye ["objective lens"] and with the mirror at your own eye, arm's length away, throw the reflected light, through the objective lens, into the patient's pupil. 3. Adjust the distance between the objective lens and the mirror, by moving the lens forward, or by coming up closer to it with the mirror, or both manouvres, until a focussed image of the patient's fundus comes into view. It is a procedure which the operator must work out for himself, but it is really much easier technic than the direct method. 4. Bear in mind that by this method we get a real, in- verted image of the fundus, magnified about 6 times. By this method, also, you can view practically the entire fundus at once, whereas by the direct method you see only a part of it at a time. 5. Now slowly withdraw the objective lens from the patient's eye, toward your own, watching the image of the optic disc. If this image of the disc remains the same size, there is no error of refraction. 6. If, on withdrawing the objective lens, the image of the disc grows smaller the patient is hyperopic, and the plus lens which makes it stay the same size as the meas- ure of the myopia. 40 TECHNIC OF REFRACTION 7. If, on withdrawing the objective lens, the image of the disc grows larger, the patient is myopic, and the minus sphere which makes it stay the same size is the measure of the myopia. 8. If the image grows larger or smaller in one merid- ian, the patient is astigmatic, and the cylinder, plus or minus, which makes it stay the same size in all meridians is the measure of the astigmatism. The direct method is best for detailed examination of different areas of the fundus. The indirect method, for a general examination of the whole fundus and the relations of its various parts. For the refractionist, in general, the indirect method is preferable. The Geneva Ophthalmoscope and Retinoscope. To use the instrument as an Ophthalmoscope : 1. Turn on the light and turn the ophthalmoscopic lens into position. Rotate dials 18 and 22 to zero, dial 16 to OPH. 2. Have patient place his chin on the chin-rest, and his forehead against the head-rest. Be sure the face sets squarely on the frame. Hold up your index finger and instruct patient to follow its movements while focussing and examining. 3. Looking past the side of the instrument, adjust it so that the black dot which represents the image of the hole in the mirror appears on the iris or sclera, and focus this dot sharply by turning handles No. 9 toward or from you, as the case may demand. [Keep patient's eyes fixed on your index finger.] TRIAL CASE AND REFRACTIVE INSTRUMENTS 41 4. Having focussed the black dot, swing the telescope of the instrument round until the dot just enters the pa- tient's pupil on the nasal side. The instrument and the patient's eye are now in proper adjustment for viewing the fundus. However, slight readjustments must be made by means of moving the index finger around [the patient following its movements] until a clear view is obtained. 5. If you yourself are presbyopic, you must wear your presbyopic correction, either in the form of glasses, or by means of the proper lens in Clip No. 32 located just back of the eye-cup. 6. With the black dot focussed as described, you are viewing the optic disc on the patient's fundus. To view other portions of the fundus, move your index finger around, as desired, and have the patient follow its move- ments. If, however, you make any considerable range of movement, it will be necessary to swing the instrument slightly, so that the patient's pupil will not go outside the area of light. N. B. Test the focussing first with a piece of white paper in place of the patient's face. If the area of light, when projected on to this paper, is not circular, it is be- cause the ophthalmoscopic lens is not in a true vertical position. To remedy this, first see that the lens is turned up as far as it will go, then turn the small screw on top of tube just over where the lens strikes when it is up, until the circle is perfectly round. 42 TECHNIC OF REFRACTION CHAPTER IV. THE OPHTHALMOMETER. By means of the ophthalmometer we are enabled to measure the degree of curvature of the cornea, and thus to determine whether it has the same curvature in all directions or not, and if not, what are the differences of curvature in the two chief meridians. In other words, it enables us to detect and to measure corneal astigmatism. The fact that there may be lenticular astigmatism pres- ent, which is not detected or measured by the ophthal- mometer, does not lessen the value of this instrument in its own field. There are three standard makes of ophthalmometer in general use, and instructions are here given for using each of them. The Universal Ophthalmometer. i. Switch on the lights before the patient is seated; otherwise the noise of the switch, or the sudden light, may startle him and cause him to move out of position. '2. Focus the instrument, by turning the adjustable eye- piece until the cross-hair-lines are seen clearly and dis- tinctly. They can be made more clearly visible by hold- ing a piece of white paper, before the end of the tele- scope while focussing. 3. Adjust the table so that, with arms folded naturally on the table the patient's chin and forehead rest easily in the frame provided for them. Instruct patient to lean his forehead against the rest, and to raise his eyebrows, so as to expose the cornea to view. TRIAL CASE AND REFRACTIVE INSTRUMENTS 43 4. Raise or lower the chin rest, by turning the knurled handle at your end of the telescope, so that patient's face is upright, and the outer canthus of each eye is in line with its respective white spot on the head-rest. This in- sures horizontal alignment of eyes and instrument. 5. Turn the dial so that both sight holes are horizontal and the figure 45 on the larger dial is at the top of the instrument. Then raise or lower the instrument, by means of the large knurled handle at your end, until the white spot at the side of the head-rest is visible through the sight-hole. Swing the blinder attached to the head-rest until it covers the eye which is not under examination. Then swing the telescope until the eye to be examined is directly before the sighthole. Instruct patient to look- steadily into the telescope. 6. Adjust the telescope, by raising or lowering or turn- ing from side to side, until the images of the mires are 44 TECHNIC OF REFRACTION located, and the central images centered on the cross hairs. (Disregard the outer images.) 7. Lock the telescope by pulling toward you the locking handle on right side of upright. 8. Turn the focussing wheel on side of telescope until the images of the mires are clear and distinct. You are now ready to begin to make observations. 9. Take hold of the rough grip section of the telescope and revolve it until the black lines running through the middle of the two mires are in one straight line. This lo- cates the first principal meridian of the eye. 10. Turn one of the pegs on the disc and turn the disc either way until the inner edge of one mire just makes contact with the inner edge of the other mire. The white double pointer now registers on the small dial the angle of the meridian, and on the larger dial its dioptric value. Make notation of these data. 11. Revolve the telescope, as before, until the middle lines of the mires are again in a straight line with each other, and again turn the disc, by means of a peg, until the inner edges of the two mires are just in contact. The white double pointer now registers on the small dial the angle of the second principal meridian, and on the larger dial its dioptric value. Make notation as be- fore. You now have the angles and dioptric values of the two principal meridians of the eye. 12. If the values of the two meridians are equal, there is no corneal astigmatism. If they are not equal, then there is an astigmatism equal to the difference between the two values. TRIAL CASE AND REFRACTIVE INSTRUMENTS 45 13. If you correct by means of minus cylinder, the power of the cylinder will be the difference between the two meridians, and the axis in the meridian of lower diop- tric value. If with plus cylinder, the power of the cylinder will still be the difference between the two meridians, but the axis will lie in the meridian of greater dioptric value. The C-I Ophthalmometer. 1. Switch on the lights, as instructed above. 2. Focus the instrument, by means of the knurled brass handle on the left side, until the images of the mires are clear and distinct. 3. Adjust the table so that, with arms folded on the table, patient's chin rests comfortably on the chin-rest and his forehead against the head-rest. See that the eyes are level, and swing the cover over the unexamined eye. 46 TECHNIC OF REFRACTION 4. Set the perforated meridian pointer to 90 deg. Sight through the perforation in the hand, and the disc, which serve as sights. Set the instrument just below the eye, then sight through the telescope, and slowly raise the in- strument until the images of the mires are seen reflected from the cornea. 5. Focus the instrument, by means of the knurled brass handle on the left side, until the images of the mire are clear and distinct. You are now ready to make observations. 6. Set the eye-piece at Primary position, and rotate the large disc containing the mires until the horizontal lines through the middle of the mires make one continuous straight line. This locates the first principal meridian. 7. Rotate the adjusting wheel on the right side of the telescope until the two spurs on the horizontal meridian line between the mires form a perfect cross. The indicators now show the angle of the first merid- ian, the radius of curvature, and the dioptric value. The angle, or axis, is read from the dial just back of the disc, the radius from the right side of the adjusting wheel fixed to the lower side of the telescope, and the dioptric value from the face of the adjusting wheel. 8. Rotate the eye-piece to Secondary position, and set the left wheel to o, at the same time holding the right wheel to form a cross. If the cornea is spherical, the spurs will be seen still to form a gross. If there is astig- matism, they will have separated, and must be again made to form a cross by turning the adjusting wheel on the right side of the telescope. TRIAL CASE AND REFRACTIVE INSTRUMENTS 47 The axis, radius of curvature, and dioptric value of the second principal meridian may now be read as be- fore. 9. The difference in values of the two meridians is registered on the left wheel ; also whether the astigmatism is with or against the rule. 10. If you correct by means of a minus cylinder, the axis must be placed in the meridian of least dioptric value. If with a plus cylinder, in the meridian of greatest diop- trism. N. B. In astigmatism against the rule, i.e., where the vertical meridian is the meridian of least refraction, the full correction indicated by the instrument will usually be acepted by the patient. But where it is with the rule, it is usually necessary to deduct somewhere in the neigh- borhood of .50 D., owing to the distance of the correcting lens from the eye. If the lens is plus, this increases its value ; if minus, it decreases it. The Meyrowitz-Javal Ophthalmometer. 1. Seat the patient comfortably. Raise or lower the chin rest until the eyes are in line with and level with the white index marks on the head rest. Cover the eye not under examination. 2. Place the arc bearing the mires to the horizontal position, with the axis-indicator pointing to zero. 3. Sight along the barrel of the telescope, and raise or lower the telescope, also swing it to left or right, as may be required, until it points at the eye to be examined. 48 TECHNIC OF REFRACTION 4. Turn on lights. Look through the telescope, and continue the adjusting movements above described until four images of the mires are seen, two being central and two on either side. Ignore the two outer images and re- gard only the two central ones. Focus the images as sharply as possible. 5. Rotate the telescope about its long axis to right or left within 45 degrees of the horizontal, until the central black lines of the two central mires are in the same straight line [though not necessarily, at this time, a con- tinuous line.] 6. Rotate the corrugated stem projecting from the mire- carrying arc until the edges of the mires are just in con- tact. The axis-indicator now registers the angle of the first chief meridian. The pointer on the parallelogram mire registers the dioptric value of this meridian on TRIAL CASE AND REFRACTIVE INSTRUMENTS 49 the scale engraved on the edge of the arc. The pointer on the step mire indicates the radius of curvature. 7. Rotate the telescope 90 degrees to the left, and again rotate the corrugated stem [if necessary] until the edges of the mires are just in contact. The axis-indicator now registers the angle of the sec- ond chief meridian ; the parallelogram pointer shows its dioptric value ; and the step-mire pointer the radius of curvature. 8. If the dioptric values of the two chief meridians are equal, or if, on rotating the telescope to the secondary position, the edges of the mires are seen to be still just in contact, there is no astigmatism. If they are not equal, then there is an astigmatism equal to the difference be- tween the two values. 9. If the mires, in the secondary position, overlap, the astigmatism is "with the rule," and calls for a plus cylin- der with its axis at the angle shown by the axis-indicator "A" or a minus cylinder with its axis as shown by the plain pointer. If the mires, in the secondary position, are separated, the astigmatism is "against the rule," calling for a minus cylinder with its axis as shown by the axis- indicator "A" or a plus cylinder with its axis as shown by the plain pointer. N. B. Only in the two chief meridians of an astig- matic eye do the central black lines of the mires form a straight line with each other. In every intermediate mer- idian they form a broken line. 50 CHAPTER V. THE PHOROPTOMETER. As the name implies, the original and essential purpose of this form of instrument is for the detection and meas- urement of muscular imbalance. However, as a matter of fact, it is a combination of apparatus for measuring ocular refraction and testing the extrinsic muscles. It is, in short, a mechanical assemblage of all the principles and materials of the trial case, in a form and arrangement which render it much more convenient and accurate than the case. There are three standard makes of this instrument in the field, and instructions are here given for each of them. The DeZeng Phorometer, Phoroptor or Phoro- Optometer. For testing refraction, proceed as follows : 1. Align the instrument vertically and horizontally with the distance chart, adjust the brow-rest or eye cups and pupillary slides to their respective positions, and the spirit- level to horizontal balance. Remove the phorometer at- tachment (if the instrument carries one), the Maddox rods, and the double rotary prisms from their positions, the former by folding forward and downward, the latter by swinging to right and left. 2. When using the phorometer trial frame instrument, place your spherical and cylindrical lenses from the trial case before the eyes, in the same manner as in the use of the ordinary trial case, the spherical lenses in the rear cells and the cylinders in the front revolving cells. TRIAL CASE AND REFRACTIVE INSTRUMENTS 51 3. When employing the Phoroptor or Phoro-Optome- ter, instead of using spherical lenses from the trial case, wheel into place before the eye the spherical lenses at- tached to the instrument, combining the lenses in the dif- ferent discs to make whatever power is desired. If the instrument does not carry a battery of cylinders, use cylindrical lenses from the trial case, placing them in the front revolving cells, and turning them to desired axes. 4. Proceed with these lenses in the manner described under TRIAL CASE. Maddox Rod Test. i. For testing the horizontal muscles, set the axis of the multiple rods horizontal (or at 180 degrees), and direct 52 TECHNIC OF REFRACTION the patient's attention to a small circle of light 20 feet distant. 2. If the vertical streak and the circle of light are sepa- rated homonymously, i.e., the streak appearing on the same side as the eye wearing the Maddox rod, the error is one of esophoria. 3. Swing the rotary prism into position, with the indi- cator set at zero. Gradually rotate the indicator down- ward and outward, producing prism-power base out, until the streak and the circle of light come together. The de- grees indicated on the scale show the amount of esophoria present. 4. If the vertical streak and the circle of light are sepa- rated heteronymously, i.e., the streak appearing on the opposite side to the eye wearing the Maddox rods, the error is exophoria. 5. Swing the left-hand rotary prism into position, with the indicator at zero, and gradually rotate the lever down- ward and inward, producing prism-power base in, until streak and circle come together. The indicator on the scale now shows the degree of exophoria. 6. For testing the vertical muscles, set the axis of the rods vertical (or at 90 degrees). 7. If the streak appears above the circle of light, right hyperphoria is indicated. If below, left hyperphoria. 8. Raise the Stevens Phorometer into place, with the indicator on the right prism set at O. (This throws the handle inside). Rotate the prisms gradually upward if there is right hyperphoria, downward if there is left hyperphoria, until the streak and the circle coincide. The TRIAL CASE AND REFRACTIVE INSTRUMENTS 53 indicator will then show the amount of error right hy- perphoria if above, left hyperphoria if below. Or the amount of the imbalance may be measured by using the rotary prism. 9. To test the oblique muscles, set the Maddox rod with its axis vertical. If the streak appears other than horizontal, there is cyclophoria. 10. Rotate the rod until the streak appears vertical. The indicator will then show the degree of error. If it stands to the nasal side, it indicates that amount of minus cyclo- phoria ; if to the temporal side, plus cyclophoria. As the above tests are all binocular, they do not dis- close which of the single muscles in the various pairs is at fault. They should therefore be followed by monocular tests. Monocular Muscle Tests. 1 . To test the lateral muscles, place a rotary prism with zero horizontal before the right eye, and rotate upward to 8 dioptres. This will dissociate the images and produce vertical diplopia. 2. If the lower, or false, image is seen directly below the upper one there is no imbalance. 3. If the lower image appears to the right of the upper there is right esophoria. 4. Swing a rotary prism with zero vertical before the left eye, and gradually rotate it outward until the two images are in vertical line with each other. The indi- cator then shows the amount of esophoria. 5. If under the previous conditions the lower image appears to the left of the upper, there is right exophoria. 54 TECHNIC OF REFRACTION 6. Swing the rotary prism with zero vertical before the left eye, as before, and gradually rotate it inward until the two images are in a vertical line. The indicator then shows the degree of exophoria. 7. Repeat the above procedure with the displacing prism of 8 dioptres, base up, before the left eye, to test for left esophoria and exophoria respectively. 8. To test the vertical muscles, place a rotary prism with zero vertical before the right eye, and rotate the prism inward to 12 dioptres. This dissociates the images, producing lateral diplopia. 9. If the two images are in the same horizontal plane there is no imbalance. 10. If the right-hand image lies below the left one there is right hyperphoria. 11. Swing a rotary prism unit with zero horizontal before the left eye and gradually rotate the prism upward until the two images lie in the same horizontal plane. The indicator then shows the amount of right hyperphoria. 12. If, under the previous conditions, the right-hand image lies above the left one there is right hypophoria, also called right cataphoria. 13. Swing a rotary prism unit, with zero horizontal, before the left eye, as before, and gradually rotate down- ward until the two images lie in the same horizontal line. Indicator then shows the amount of right hypophoria. 14. Repeat the above procedure with the displacing prism of 12 dioptres, base in, before the left eye, to test for left hyperphoria and hypophoria respectively. TRIAL CASE AND REFRACTIVE INSTRUMENTS 55 15. To test the oblique muscles, place a double rotary prism with zero horizontal before the right eye and rotate upward to 8 dioptres to produce diplopia. 16. Place a Maddox rod before both eyes with the axes vertical or at 90 degrees. 17. If two streaks of light are seen, one lying below the other, parallel to each other, there is no cyclophoria. 1 8. If the upper streak, seen by the left eye, appears horizontal, and the lower streak, seen by the right eye, is oblique, dipping toward the left, there is right plus cyclophoria. 19. If the upper streak is horizontal and the lower streak dips toward the right, there is right minus cyclo- phoria. 20. Repeat the procedure with the displacing prism before the left eye. 21. If the two streaks are parallel there is no cyclo- phoria. 22. If the upper streak is horizontal and the lower one clips to the right, there is left plus cyclophoria. 23. If the upper streak is horizontal while the lower one dips to the left, there is left minus cyclophoria. 24. In any of the above cases, rotate the rod over the cyclophoric eye until the lines are parallel, and the indi- cator then shows the degree of cyclophoria existing. Duction Tests. In performing these tests, begin by clearing the instru- ment of all except the correcting lenses if these are to be used. 56 TECHNIC OF REFRACTION 1. To test the internal recti, place a double rotary prism with zero vertical before the right eye, and slowly rotate the prism outward until the circle of light separates into two. Indicator shows the degree of right adduction. 2. Repeat the test with the rotary prisms before the left eye. Indicator shows the amount of left adduction. 3. To test the external recti, place rotary prism with zero vertical before the right eye and slowly rotate inward until the light breaks. Indicator shows degree of ab- duction. 4. Repeat the procedure with the prism before the left eye. Indicator shows the amount of left abduction. 5. To test the superior rectus, place prism with zero horizontal before the right eye and gradually rotate up- ward until the light breaks. Indicator shows the degree of right superduction. 6. Repeat the test with the prism before the left eye. Indicator registers degree of left superduction. 7. Place prism with zero horizontal before the right eye and gradually rotate prisms downward until the light breaks. Indicator registers degree of right subduction. 8. Repeat the test with the rotary prism before the left eye, and indicator will show amount of left subduction. 9. To test oblique muscles, place a Maddox rod before each eye, axis horizontal, with the indicator at zero. 10. Gradually rotate the right-eye rod downward (nasal side) until the parallelism of the lines breaks, forming a cross. The indicator shows the amount of right minus cycloduction. TRIAL CASE AND REFRACTIVE INSTRUMENTS 57 11. Repeat the process, rotating the left-eye rod down- ward (nasal side) until the line breaks. Indicator shows degree of left minus cycloduction. 12. Rotate the right rod downward (temporal side) until the line breaks. Indicator shows the degree of right plus cycloduction. 13. Repeat the test with the left eye, rotating rod downward (temporal side) until the line breaks. Indi- cator shows the degree of left plus cycloduction. Muscle Exercises. The procedure for exercising the ocular muscles is the same as in the duction tests. The Ski-Optometer. 1. Place the instrument in position, assuring yourself of its horizontal status by means of the spirit level. 2. Adjust the inter-pupillary distance by aligning each eye individually. Do this by drawing an imaginary ver- tical line downward from the cp-degree point on the axis scale through the center of the pupil. 3. Place the opaque disc before the eye not to be tested by setting the supplementary disc handle at "shut." 4. Set the lens battery at "open." With the first turn of the spherical lens battery toward the nasal side, a plus 6 D. sphere is placed in position. This will "fog" the average patient. 5. Gradually reduce the plus sphere by means of suc- cessive turns of the battery toward the nasal side until the 58 TECHNIC OF REFRACTION astigmatic wheel chart just becomes visible. If all spokes of the wheel are equally visible and clear there is no astigmatism. If one spoke stands out clearer than the rest there is astigmatism, in which case proceed as fol- lows: 6. Set the axis indicator at the same angle as repre- sented by the line in the astigmatic chart seen most clearly by patient. This insures every cylinder to be used auto- matically positioning itself at this axis. 7. Beginning with the weakest (minus) cylinder, swing successively stronger cylinders before the eye until all lines in the astigmatic chart become equally clear. The astigmatism is measured and corrected by this cylinder. 8. Now continue to reduce the plus sphere power by TRIAL CASE AND REFRACTIVE INSTRUMENTS 59 successive turns toward the nasal side until patient reads 20/20 on the type chart. The total lens power, sphere and cylinder, now before the eye is the measure and cor- rection of the error. 9. If, in working from the plus spherical scale, the "zero" mark is reached and patient is still unable to read 20/20 (i. e., patient is myopic), set battery at "open" again and gradually rotate toward the temporal side, thus gradually increasing minus spherical power until 20/20 is read. 10. If, when item 5 is completed, there appears no astigmatism, items 6 and 7 are omitted. Binocular Muscle Tests. 1. To make tests of the lateral muscles, set the white lines of the red Maddox rod either at white zero or at i8o-degree line, with the rods in horizontal position, and the phorometer on the white neutral line, with handle horizontal. 2. If the red streak of light appears vertical, running through the spot of light, there is no imbalance. 3. If the red streak does not bisect the spot of light there is esophoria or exophoria. Rotate the handle, and if the streak and the spot move closer together, keep on rotating it in that direction until the streak bisects the spot. If, on rotating the handle, the streak and spot sep- arate further, reverse the rotation of the handle until the streak bisects the spot. The indicator on the phorometer will register on the white scale whether the error is esophoria or exophoria, and how much. 60 TECHNIC OF REFRACTION In testing the lateral muscles, ignore the red scale and employ only the white scale. 4. To test the vertical muscles, set the single white line of the Maddox rod, or the indicator, on red zero and the pointer of the phorometer on the neutral line of the red scale with the handle pointing upward. 5. If the red streak appears horizontal, bisecting the spot of light, there is no imbalance. 6. If the streak does not bisect the spot there is hyper- phoria or hypophoria. Rotate the handle, as above, until the streak bisects the spot. At the point of bisection the indicator will show the degree of error. In testing the vertical muscles, employ the red scale alone, ignoring the white scale. N. B. The above tests, being binocular, give no infor- mation as to which single muscle is at fault. They should therefore be followed by monocular duction tests. Monocular Duction Tests. Remove the Maddox rod and the phorometer from operative position during these tests, leaving the correct- ing lenses in place if required. 1. To test adduction of the right eye, place the rotary prism battery before this eye, with the prism indicator at zero on the prism upper scale. Place the two cyphers (o's) in vertical position with the handle pointing hori- zontally. 2. Slowly rotate the rotary prism outward until the largest letter on the type, or the Greek cross, doubles. The reading on the scale represents the degree of adduction. TRIAL CASE AND REFRACTIVE INSTRUMENTS 61 3. To test the adduction of the left eye, repeat the process with the rotary prism battery before the left eye. 4. To test abduction of the right eye, set the battery before that eye, exactly as described in item i, and slowly rotate the prisms inward until the letter or the cross doubles. The reading on the scale represents amount of abduction. 5. To test left abduction, repeat the procedure with the rotary prism battery before the left eye. 6. To test superduction of the right eye, place the rotary prism battery before the right eye with the two cyphers lying horizontally and the handle pointing ver- tically. 7. Slowly rotate the prisms downward until the letter or the Greek cross breaks. The indicator shows the de- gree of right superduction. 8. To test superduction of the left eye, repeat the process with the prism battery before the left eye. 9. To test subduction of the right eye, place the prism battery before the right eye as described in item 6 and slowly rotate the prisms upward until the letter or the cross breaks. Indicator shows the degree of right sub- duction. 10. To test subduction of the left eye, repeat the process with the prism battery before the left eye. Muscle Exercises. The procedure for exercising the ocular muscles is the same as in the duction tests. 62 TECHNIC OF REFRACTION The Genothalmic Refractor. i. Adjust the horizontal balance of the instrument by means of the spirit level which is worked by the thumb screw at back of instrument. Adjust the pupillary dis- tance by means of the lever in front and at top of disc. Fit the eyecups which act as brow rests to the patient's eyes (these cups are detachable and can be sterilized be- tween usages). Remove phorometer attachment, Mad- dox rods and rotary prisms from their position by raising them out of range. 2. Tilt instrument slightly in at bottom to eliminate reflections when using retinoscope. 3. To place spherical lens powers before the eye, turn the knurled knob which is below and a little to the outside of the apertures. The dial registers the strength of lens before the eye. Temporal turn of the knurled knobs increases, nasal turn decreases power of lenses. Plus spheres to 17.75 D. in quarters, minus spheres to 18.00 D. in quarters. To secure minus powers turn auxiliary lens to minus p.oo and proceed by decreasing with plus 8.75. Stronger than minus 9.00, turn auxiliary lens to minus 18.00 and proceed in a like manner. 4. To place cylinders before the eye, turn the knurled knob which is at the outer edge of the large disc. Minus cylinders to 3.75 D. in quarters. Auxiliary cell in back of instrument for powers over 3.75 D. or eighths. Dial registers the cylinder power in position. To set axis of the cylinder push down lever at the outer side of instrument and turn to desired angle. Automatic adjustment locks it in place when released. 5. Proceed with these batteries of spherical and cylin- drical lenses as you would with lenses from the trial case. Maddox Rod Test. T. Lower one or both of the Maddox rods into position before the aperture or apertures. 2. To test the lateral muscles set axis of rod at 180 degrees, directing patient's attention to spot of light. 3. If streak passes directly through the spot of light there is no vertical imbalance. 4. If they are separated the streak appearing on the opposite side of eye wearing the Maddox rod there is exophoria. 5. With Maddox rod at 180 over right eye, lower rotary prism over left eye into position with indicator at zero vertical. If streak is displaced to the left of the spot of light, rotate the indicator producing prism base in until streak passes through spot of light, indicator registering amount of exophoria. 6. If they are separated the streak appearing on the 4 TECHNIC OF REFRACTION same side of the eye wearing the Maddox rod there is esophoria. 7. With Maddox rod at 180 over right eye, lower rotary prism over left eye into position with indicator at zero vertical. If streak is displaced to the right of the spot of light rotate the indicator outward, producing prism base out until streak passes through spot of light, indicator registering amount of esophoria. 8. To test vertical imbalance, set axis of rod vertical. 9. If streak and spot are in the same horizontal plane there is no imbalance. 10. If streak appears above spot there is right hyper- phoria ; if below it, there is left hyperphoria. 11. Lower the Stevens phorometer into position, with indicator on right prism set at zero. Rotate the prisms gradually upward if there is right hyperphoria, down- ward if there is left hyperphoria, until streak and spot coincide. Indicator will show the amount of error right hyperphoria if above, left hyperphoria if below. Or the error may be measured by rotary prisms. 12. To test oblique muscles, set both Maddox rods with axis vertical. If streaks appear other than horizontal there is cyclophoria. 13. Rotate one or both rods until the streaks appear parallel. Indicator, or indicators added together, indicate amount of cyclophoria. If to the nasal side, minus cyclo- phoria ; if to the temporal side, plus cyclophoria. Monocular Muscle Tests. i. To test lateral muscles, place a rotary prism, zero horizontal, before the right eye and rotate upward about 8 dioptres, to produce diplopia. TRIAL CASE AND REFRACTIVE INSTRUMENTS 65 2. If the lower (false) image appears directly below the upper (true) image, there is no imbalance. 3. If the lower image appears to the right of the upper there is right esophoria. 4. Place a rotary prism, zero vertical, before the left eye and slowly rotate it until both images are in vertical line with each other. Indicator shows amount of esophoria. 5. If, under conditions of item i, the lower image appears to the left of the upper, there is right exophoria. 6. Place a rotary prism, zero vertical, before the right eye and slowly rotate it until the images are in vertical line with each other. Indicator shows amount of right exophoria. 7. Repeat the above procedures with the left eye to test for left esophoria and exophoria, respectively. 8. To test the vertical muscles, place a rotary prism, zero vertical, before the right eye and rotate inward to 12 dioptres to produce diplopia. 9. If the two images are in horizontal line with each other there is no imbalance. 10. If the right image is below the left one there is right hyperphoria. 11. Place a rotary prism, zero horizontal, before the left eye, and rotate upward until the two images come into horizontal line. Indicator shows degree of right hyperphoria. 12. If the right image is above the left there is right cataphoria. 13. Place a rotary prism, zero horizontal, before the left eye, and rotate downward until the images come into 66 TECHNIC OF REFRACTION horizontal line. Indicator shows degree of right cata- phoria. 14. Repeat process with left eye. 15. To test oblique muscles place rotary prism indi- cator zero vertical before the right eye, rotate indicator to 12 prism dioptres to produce diplopia. 16. Place both Maddox rods before the eyes, axis 90 degrees. 17. If the two streaks of light appear other than paral- lel, there is cyclophoria. 18. Rotate one rod until the streaks become parallel. Indicator will show amount of cyclophoria. If to the nasal side, it shows minus cyclophoria ; if to the tem- poral side, plus. 19. Repeat the procedure with the left eye. The Tropometer. This is an instrument for measuring the range of move- ments of the ocular muscles. 1. Seat the patient in a chair adjusted to such a height that his forehead may be comfortably maintained against the brow piece of the head rest, with the face in an up- right position. Instruct him to take the wooden bit be- tween the teeth, and more the stirrup carrying this bit in or out and up or down, as necessary to secure the position mentioned above. 2. Hinged to the head-rest is an approximately semi- circular shaped bar. Swing this over the patient's head and push the adjustable bar at the back forward so that its round, flat termination is pressed firmly against the back of the head, making movement impossible. TRIAL CASE AND REFRACTIVE INSTRUMENTS 67 3. Immediately in front of the patient's face is a small fixture carrying two arms, one with a flat and one with a round terminal. These may be moved in and out and up and down, and the distance between them may be varied. Adjust these so that one of them rests on the bridge of the nose and the other of them in the middle nf the upper lip below the nose. Measuring the Ocular Movements. 4. Turn the Telescope at right angles to the patient's line of vision and so that the window in the square box may be pointed as presented to the patient's eye. 5. Adjust the height of the Telescope by means of the hand wheel at the side of the column. Focus the picture 68 TECHNIC OF REFRACTION of the eye seen through the Telescope, by means of the hand wheel at the side of the Telescope, and the scale in the eyepiece by turning the eyepiece to the right or left, as may be required. 6. Immediately in front of the eyepiece and projecting from the body of the Telescope is a small handle. Adjust the scale horizontally or vertically by means of this projection. 7. After the patient's head is fixed, move the Telescope to the right or left until an image of the patient's eye is seen. Sharply focus this image and also the scale. 8. To measure the vertical excursion of the eye, turn the scale so that the divisions on it are horizontal. Raise or lower the Telescope until one of the scale divisions coincides with the Corneal Meridian. Ask the patient to look up. Note the excursion of this point of reference. Ask the patient to look down and notice how far along the scale the Corneal Meridian travels before it stops. 9. To measure a lateral excursion locate the scale so that the lines are vertical. Swing the Telescope to the right or left until one of these lines is coincident with the Corneal Meridian and ask the patient to look first to the right and then to the left and notice the angular excur- sion of the eye on the scale division. TRIAL CASE AND REFRACTIVE INSTRUMENTS 69 CHAPTER VI. THE PERIMETER OR CAMPIMETER. This instrument is for the purpose of mapping out the visual or retinal field. The essential principle is the same in every make of instrument. While the patient fixes a central fixation point, a small test-object is moved either from the periphery of an arc toward this central point or from the central point toward the periphery. The place where the test object, being thus moved, comes into the patient's indirect vision, or passes out of vision, marks the limit of the retinal field in that meridian. The test is repeated in every meridian, successively, thus giving a contour of the retinal field. The chief differences between campimeters is that, whereas the older forms are monocular, the later models are binocular or stereoscopic. Standard Registering Perimeter. J . Put the chart in place in the chart-holder behind the metal arc. 2. Seat the patient comfortably before the instrument so that his chin rests easily on the chin rest. Instruct him 70 TECHNIC OF REFRACTION to fix the central fixation mark on the target. Blank the left eye. 3. Explore the visual field by moving the test object (fitted on to the long handle) from the center of the target out along the metal arc toward the periphery until the patient, who continues to fix the center, can no longer see the object. When this point is reached, indicate it on the chart by punching it through the perforation in the metal arc. 4. Revolve the metal arc to each meridian, successively, and repeat the test in each meridian. 5. When all meridians have been thus tested and marked, take out the chart and join up, with a pencil or pen, the punch marks in the chart. The result will show the visual field. 6. Repeat the process for the left eye. The Stereo-Campimeter. By means of this instrument the field of vision can be outlined with the patient exercising binocular fixation which, for many reasons, is greatly superior to monocular fixation. 1. Adjust the instrument, by means of the elevating device and the hinge, to suit the position and comfort of the patient. 2. Place the test charts, as they may be used, sym- metrically and axially with respect to the center of the stereo lens system by making the middle of the chart coincide with the zero mark on the millimeter scale on the object stage. 3. Set the optical centers of the stereo lens system 80 TRIAL CASE AND REFRACTIVE INSTRUMENTS 71 mm. apart, so as to coincide with the fixing centers of the test charts. 4. Instruct the patient to fix the black and red lines. If the short red line appears above or below the center of the horizontal black line, there is hypophoria. Correct it by means of the rotation stereo prisms. 5. If the vertical red line bisects the black scale at figure 8 there is no lateral imbalance. If not, there is imbalance. Correct it by means of the additional prisms, inserted in the metal grooves. 6. Now direct the patient's attention to the octagonal form on the chart. (There should appear but one octa- 72 TECHNIC OF REFRACTION gon. ) Explore the field of vision by moving the various test objects from the center of the octagon outward until patient loses sight of them, doing this in the various meridians and noting on the charf the point in each meridian where the object vanishes. Join these points on the chart; to make the contour of the visual field, and compare it with the normal figure. 7. To outline blind spot areas of large angular extent, remove the metal cross bars and place the Lloyd slate upon the object-stage by means of the two metal grooves in the slate which fit the object-stage. Be sure to push the slate snugly home so that the slate may be in correct relation with the stereo lens system. Outline the areas as described in section 6. TRIAL CASE AND REFRACTIVE INSTRUMENTS 73 CHAPTER VII. TESTS FOR COLOR BLINDNESS. For very accurate, scientific testing of color sense a spectroscope is necessary to determine whether or not the spectrum is shortened, to the patient's vision, at the red end, and also, by isolating the bands of color, to discover how the patient sees and compares the single colors. Foi ordinary purposes, however, one or other of the following tests are employed. Holmgren's Wool Test. This test is carried out by means of a definite series of colored skeins of worsted. The principle of the test is that red and green blind persons see in the spectrum only two colors, yellow and blue, with a neutral gray zone between them. Green is the first test color because it corresponds in tint to the neutral zone, thus making an excellent confusion color with pale shades of gray, brown and yellow. Rose is the second, being a mixture of red and blue in which, of course, the color-blind person sees only blue. Red is the third, which affords an excellent confusion with dark shades of brown and gray. Test i. Ask the patient to select from the entire col- lection of skeins, placed in good daylight, all the colors which in general hue seem to him like the large green skein. The completely color-blind will select, with or without the greens, some confusion colors, such as grays, fawns, pinks, yellows. The incompletely color-blind will match it with greens, to which they will add a few light shades of fawn or gray. This test indicates whether or 74 TECHNIC OF REFRACTION not the patient is color-blind, completely or incompletely. For further investigation employ another test. Test. 2. Mix the colors up again and ask the patient to match the rose skein. The color-blind will select always the light or dark shades of blue and violet. The com- pletely color-blind will choose blue or violet, with or with- out purple. The green-blind will select green or gray, without purple. A patient proven color-blind by Test i is only incompletely so if he matches rose with deep pur- ples alone. Test 3. Ask the patient to match the red skein. The red-blind will select red and the shades darker than red; the green-blind, green and brown shades lighter than red. Only markedly color-blind persons fall down on this test. Jennings' Self-Recording Test. This is a modification of the Holmgren test. It con- sists of a square box, divided into two compartments, one for the green and one for the rose test. The standard skeins of green and rose, respectively, are attached to the inside of the box lid, and in each compartment is a color board, made up of the green and green-confusion colors on one side, and of rose and rose-confusion colors on the other side. Proceed with the tests exactly as under the Holmgren method, except that the patient, instead of laying the skeins together, indicates his choice by thrusting a stylus into the perforated hole in the center of each color on the color board. TRIAL CASE AND REFRACTIVE INSTRUMENTS 75 Beneath the color board is a record sheet, divided into squares corresponding to the color patches and marked with a G and an R, respectively, in those squares which match the green and the rose, respectively. If the patient be normal there will be a punch-mark on the record sheet in every square marked G and R. Any punch mark in a blank space indicates a mistake. If the mistake is on a horizontal line with the letter G the mis- take was made in the green test ; if horizontal with R it was made in the rose test. Williams' Lantern Test. This test has two specific aims : ( i ) To test the color perception in the central retinal area, where light from a distant lantern focuses, and (2) to determine the ability of the person to recognize and name the colors of signals which have to be used at night. In the worsted test no names are used, but only colors ; in this test it is impor- tant that the candidate be able to give to color sensations the names which normal persons give to them. It is, therefore, particularly applicable to railroad men. The lantern, screened by shutters, is lighted in a dark- ened room and the colored glasses made to face the candi- date. By means of revolving shutters the colored lights are revealed to him. Show the colors, two or three at a time, in the sequence of the standard record form used, and require him to call out the names of the colors. Where he names the color correctly, write O. K. against it on the record ; where he names it wrongly, write in the name that he gives. 76 TECHNIC OF REFRACTION Reject the candidate for signal service: If he calls a red light green or white; If he calls a green light red or white; If he calls a white light red or green. N. B. Persons are sometimes able to differentiate colors by their luminosity. To obviate this, vary the in- tensity of the lights during the test. It is very important that during the Williams' test you make no remark which will indicate whether the candi- date's answer is right or wrong. Nagel's Test. This consists of a set of cards, each bearing a series of little color discs arranged in a ring. In some rings the discs are all of the same color but in different shades ; in others there are two or three different colors. Ask the patient to indicate which of the rings are mono- chromatic, which dichromatic and which trichromatic. His answers will quickly disclose the existence and nature of his color-blindness. TRIAL CASE AND REFRACTIVE INSTRUMENTS 77 CHAPTER VIII. MISCELLANEOUS. The Punctumeter. By means of this instrument, the working principle of which is the substitution of the focal length of a lens for the lens itself, hyperopia, myopia, astigmatism and accom- modation can all be measured. To measure hyperopia or myopia : i. Place the letter target before the eye and set the target holder out to the plus 5 D. mark on the scale. This will fog the ordinary patient. 2. Move the target slowly in toward the patient's eye until the small letters can be read. Then very slowly and gradually move it outward again, ^ D. at a time, as long as the letters can be discerned. The furthest point at which they can be seen denotes the far point. 3. The amount of hyperopia or myopia can now be read from the scale on the right side of the bar, hyperopia being marked on the further side of the zero mark, myopia on the near side. 4. In order to arrive at latent hyperopia, compare the 78 TECHNIC OF REFRACTION amount of error registered on the instrument with the amount of the patient's accommodation and his age. To measure astigmatism : 1. Place the radiating line target before the eye and set the target out at the 5 D. mark on the scale, to fog the patient. 2. Move the target slowly in toward the patient's eye until one of the radiating lines comes into vision, and ask the patient to tell the number of this line. The axis of this line indicates the meridian of least curvature in patient's eye. The line at right angles to this represents the meridian of greatest curvature. 3. Now place the cross-line target before the eye, with its cross lines coinciding with the two chief meridians just determined. 4. Move the target outward as far as possible so that the patient can still see one set of lines. Then move the supplementary slide forward and fix it by set-screw against the target slide. Direct the patient to look at the other set of lines and move the target holder in toward the eye until these lines are seen distinctly. The distance between the two slides will then indicate the astigmatic error and the power of the correcting cylinder. To measure accommodation: 1. Correct any existing astigmatism and find the far point as described in section 2 under "To measure hyper- opia or myopia." Move up the supplementary slide and fix it with a set-screw at this point. 2. Gradually move the target slide inward toward TRIAL CASE AND REFRACTIVE INSTRUMENTS 79 patient's eye to the nearest point at which small letters can be read. This indicates the near point. 3. The number of whole dioptres and fractions of a dioptre between the two slides then indicates the total amplitude of accommodation. To measure presbyopia : 1. Find the nearest point at which the target can be placed to the eye and the patient still read the smallest letters. 2. The marking on the scale at the'left side of the bar. at the point where the target holder stands, indicates the amount of reading correction for 33 cm. or 13 inches. 3. If glasses are required for a distance more or less than this, a proper amount of plus correction must be subtracted from, or added to, the figure shown on the bar. The Ametropometer. i. Adjust the stool or chair so that the patient's eyes will be at the same height as the eyepiece of the instru- 80 TECHNIC OF REFRACTION ment. Instruct patient to place the eye that is being tested close to the eyepiece, with head erect. If his error or refraction is too great for him to see the rings on the chart, place a plus or minus sphere in the cell which will enable him to see two rings. 2. If patient is emmetropic he will see two white rings whose outer edges will just touch at all meridians as the disc of the instrument is revolved. 3. If patient is hyperopic, the edges of the white rings, as the disc is revolved, will be separated at all meridians. The plus sphere which makes them just touch at all meridians is the measure and correction of the error. 4. If patient is myopic, the edges of the white rings, upon revolving the disc, will overlap in all meridians. The minus sphere which causes them to just touch in all meridians is the measure and correction of the myopia. 5. If the edges of the rings just touch at one meridian and separate the opposite meridian, patient has simple hyperopic astigmatism. The plus lens, with its axis as indicated by the pointer D, which makes the edges just touch in all meridians, is the measure and correction of the error. 6. If the edges of the rings just touch in one meridian and overlap in the opposite one, patient has simple myopic astigmatism and the cylindrical minus lens which causes them to just touch in all meridians, is the measure and correction of the error. 7. If the rings are separated in all meridians but have a meridian of greatest and least separation, patient has TRIAL CASE AND REFRACTIVE INSTRUMENTS 81 compound hyperopic astigmatism. First find a plus cylin- der, with its axis as indicated by the pointer D, which renders the separation equal in all meridians ; then a plus sphere which causes the edges to just touch in all merid- ians. This combination is the patient's proper correction. 8. If the rings overlap in all meridians but have a meridian of greatest and least overlapping, patient has compound myopic astigmatism. First find a minus cylin- der which, with its axis as indicated by the pointer D, will render the overlapping equal in all meridians; then a minus sphere which causes the edges to just touch in all meridians. This combination is the patient's proper cor- rection. 9. If the rings are separated in one meridian and over- lap in the opposite meridian, patient has mixed astigma- tism. First find a cylinder, plus or minus, which, with its axis as indicated by the pointer, will render the sep- aration or the overlapping, as the case may be, equal in all meridians ; then a sphere of opposite curvature to the cylinder which will cause the edges to just touch in all meridians. This combination is the proper correction. The Dynamic Refractor. The technique of this instrument is exceedingly simple, as follows : 1. Instruct the patient to look through the eye-prisms and fix the chart. Two sets of lines, red circles and arrows will appear, one below the other. 2. If the lower arrow stands between C and D, to the right on the upper line, accommodation and convergence 82 TECHNIC OF REFRACTION are in harmony and the refraction of the eye is normal. 3. If the lower arrow stands further to the right than E, there is myopia, and the minus sphere which makes it stand at the normal position, i. e., between C and D, is the correction. 4. If the lower arrow stands to the left of the normal position, i. e., to the left of C, there is hyperopia, and the plus sphere which makes it take the normal position be- tween C and D is the measure of the error. 5. If the lower red circle is bisected by the horizontal upper line there is no imbalance of the vertical muscles. 6. If the lower red circle is above the upper line there is right hyperphoria; if below it, there is left hyper- phoria. The prism which, with its base up or down, as the case may be, causes the line to bisect the circle, is the measure of the vertical imbalance. TRIAL CASE AND REFRACTIVE INSTRUMENTS 88 Interpupillary Gauge. For measuring the interpupillary distance: i. With the bridge at one end of the tubes resting on the bridge of the patient's nose, properly centered, and your own eyes applied to the shaded eyepiece at the other end, instruct the patient to fix the fixation mark with his right eye. Read the millimeter marks on the two scales above and below the center of the patient's pupil. 2. Pull the shutter-lid until the right tube closes and the left one opens. Repeat the procedure with the patient's left eye, reading the two scales, above and below, as before. 3. The reading on the upper scale in each case gives the pupillary distance from the center of the bridge for distance glasses. The reading on the lower scale for each eye gives the pupillary distance from the center of the bridge for reading glasses. 4. It is advisable to make two or three readings in each case and take the average as your finding. 84 TECHNIC OF REFRACTION The Placidoscope. 1. Place the patient with his back to the light. Seat yourself at a convenient distance in front of him and hold the disc before your eye in the same manner as a retino- scope, looking through the peep-hole. 2. The reflected image of the disc will appear on the patient's cornea in the form of a concentric set of rings. 3. If the reflected rings appear circular there is no corneal astigmatism. If they appear elliptical, there is astigmatism with the long axis of the ellipse correspond- ing to the meridian of least curvature. 4. Use this device to detect irregular astigmatism and conical cornea. TRIAL CASE AND REFRACTIVE INSTRUMENTS 85 CHAPTER IX. THE COMPLETE EXAMINATION AND RECORD. Every refractionist, of course, has his own method and order of procedure which he works out for himself from his own experience and which is undoubtedly the best for him. It is obviously beside the mark to be dogmatic in such a matter or to insist that this or that course is the ideal one. The important things are [i] that the refrac- tionist should have a definite, orderly mode of procedure to which [with detailed variations, as occasion may de- mand] he adheres, for nothing weakens the patient's faith in the operator and the operator's confidence in himself like aimless pottering, and [2] that the patient be given a complete and thorough examination, by means of every method and appliance which modern science has placed at the operator's disposal, and an intelligent record made of all the findings in the case. The mode of procedure here set forth is necessarily that which the author, from his own experience, from his observation of others' experience, and from his knowledge of the principles involved, has found to be the most prac- ticable and productive of the best results. Vision and Visual Acuity. Clearly, the first thing to do is to ascertain what is the patient's vision, without any help or correction, with each eye separately and with both eyes together. This may be done either by Bonder's method, i. e., by means of the Snellen type chart at 20 feet, the vision being recorded as a vulgar fraction, of which 20 [the normal] is the num- erator, and the lowest line which can be read by the pa- 86 TECHNIC OF REFRACTION tient is the denominator, or by the Ives Visual Acuity Test, in which the vision is recorded as it appears on the scale. Thus, if by Bonder's method the patient reads the 40 line with the right eye alone, the 50 line with the left eye alone and the 30 line with both eyes, the record will be : O. D. 20/40 O. S. 20/50 O. U. 20/30 Bear in mind that the result of this test does not neces- TRIAL CASE AND REFRACTIVE INSTRUMENTS 87 sarily give the patient's visual acuity, but only his vision, expressed in the same terms as we express visual acuity. The vision, without glasses, and the actual visual acuity may be the same thing or they may not. In most refrac- tive cases they are not, for in most instances the patient's actual visual acuity is normal, as will appear as soon as he is relieved of the handicap of refractive error. Actual visual acuity can be determined only after refraction has been rendered emmetropic by the best possible lens cor- rection. Whatever defect in vision then remains is attributable to a true lowering of visual [retinal] acuity. This test should therefore be repeated when the patient's refraction has been completed. Certain tentative conclusions may be reached from the results of the vision test which suggest the lines the re- fraction tests should take. These conclusions, however, must not be taken too seriously, as they often mislead. Thus, if the patient reads 20/20 or better, it seems pretty certain that any refractive error he may prove to have will be of a hyperopic nature; if, on the contrary, he cannot read anything like 20/20 say only 20/50 it is probable his error is in the domain of myopia or astig- matism. However, high hyperopes often are unable to read more than 25/50, owing to the smallness of the image made upon the retina. On the whole, it is perhaps better to pay no attention to these tentative conclusions but proceed in regular form in each case. If the vision without lenses registers normal it is highly improbable that any physical disease of the f undus is present and the ophthalmoscopic examination, in such cases, may well be omitted. 88 If the vision registers subnormal, some refractionists here advocate and practice the use of the ophthalmoscope, to determine at once whether any or all of this subnor- mality be due to a physical condition of the fundus. Personally, the author does not favor its use at this point, but recommends that the refraction of the eyes be pro- ceeded with, and if, on completion of refraction, with its best possible correction on, the eye still registers subnor- mal acuity, an ophthalmoscopic examination be then made. The reason for this order of procedure is that an ophthalmoscopic examination is very trying to the patient and often renders any refractive examination impossible at that sitting. For the same reason the author, contrary to most authorities, does not advocate making a retinoscopic test first, in spite of the valuable fore-knowledge which it affords the refractionist of the metropic conditions, un- less the subjective tests are to be omitted altogether and the operator intends to rely wholly upon objective findings. The same holds good of the ophthalmometer. Subjective Tests. When these are to be used at all and in the author's opinion both subjective and objective tests should be em- ployed in every case they should next be proceeded with. Which of these and how many of them are to be used is a matter for the operator's judgment. They are, in fact, the logical extension and development of the visual acuity test, carrying it into more detail. Which of the subjective tests or how many of them are to be used is a matter for the operator's judgment. TRIAL CASE AND REFRACTIVE INSTRUMENTS 89 As between the Fogging Test and the Stenopaic Slit, it may said, in general, that the former lends itself better to hyperopic cases and the latter to myopic; but both are often valuable in either case. The Cobalt Test should be used in every instance. In recording the subjective tests, the findings of the isst should be set down and not merely the net corrective results. Thus, in the Fogging Test, the meridianal line [if any] which stands out earliest and blackest, should be recorded, and the power and axis of the minus cylinder which equalizes the lines. In the Stenopaic Test, the meridian of best and worst vision and the spherical cor- rection for each should be set down. In the Cobalt Test each separate appearance of the light and its correction should appear on the record. The Punctumeter, the Ametropometer or the Dynamic Refractor may be added or substituted for any of the above subjective tests, each finding being properly re- corded as the test proceeds. Objective Tests. Having now ascertained the patient's subjective condi- tions in their entirety, objective tests are in order. Corneal astigmatism is first determined and measured by means of the ophthalmometer and faithfully recorded just as it appears, not [as some are in the habit of doing" as the operator thinks he will presently modify it. The retinoscope should then be used by the static method. Here again the findings should be recorded for each meridian that is shadowed and not the final cor- rective results. 90 TECHNIC OF REFRACTION Muscle Tests. These should now be taken up and performed with the greatest system and thoroughness, both as to the examina- tion and as to the record. They may be carried out either with the trial case, Maddox rod and near convergence chart, or by means of the phoroptometer. First ascertain the duction power of each muscle and pair of muscles without correcting lenses. Next investigate the state of muscle balance [or im- balance] and the accommodation-convergence relation, both for far and near point, with static correction on. Of all the phases of examination, the muscle tests call for the most detailed and complete record of findings. The practice embodied in certain record-cards of record- ing muscle findings in a single line is a very futile and misleading one. The result of each separate test for each separate muscle and pairs of muscles, must be plainly and diagrammatically set down if the record is to be of any diagnostic value. The Near Point. No refractive examination is complete without an in- vestigation of the accommodation and the near point, which should never be taken for granted, whatever the age of the patient, as insufficiencies and anomalies of ac- commodation are very common, even in young adults and children. Indeed, the term "presbyopia" and the classifi- cation of patients as "presbyopes" had best be left out of the refractionist's category altogether and every patient's accommodation and near point investigated sheerly on its own basis. All near point tests should be conducted with the patient TRIAL CASE AND REFRACTIVE INSTRUMENTS 91 wearing his distance correction, previously ascertained. The first rough determination of the near point may be made by means of Jaeger's test type or some similar TYPE FOB TESTING THE SIGHT |MIJhXnHftn7t C Bn<1K1|rJw>!Vll rV*?l5u tSt'Z distance ln>. there I* the advantage of having the reading portion placed at right angle, to the line Of vleton InstMd of In a tlanting pO.tlt.on. a* in jlvan by the ordinary style of bifocal lenses. They also remove, to a great extent. the reflections which annoy so many per- chart and translated into dioptres to indicate, approxi- mately, the patient's available accommodation. Subjectively, this finding should be confirmed and de- fined by means of the cross-cylinders. Objectively, by dynamic retinoscopy. This, as stated in the section on that subject, is the principal value of dynamic retinoscopy. Correction and Confirmation. With all the data in hand which has been derived from the foregoing procedure, the refractionist is now in a position to exercise his judgment as to just what lens cor- rection the patient shall wear and what, if anything, shall be done with the ocular muscles. With this phase of the 92 TECHNIC OF REFRACTION matter, of course, this little book of technic has nothing to do. Having decided upon the correction, it should now be placed in front of the patient's eyes and its accuracy con- firmed by means of the dynamic refractor or by re- subjecting the patient to the visual acuity^ tests, both dis- tant and near, testing each eye separately and both eyes together, as was done at the beginning of the examination, and carefully recording the findings under correction. The refractionist now has a complete case, both as to examination and also as to record. If vision, with cor- rection on, is 20/20 and comfortable, he may regard the case as being satisfactorily disposed of, at least until the patient has worn his correction for several weeks, when a review of the case may be made. The Ophthalmoscope. If, after the refraction has been worked out as thor- oughly as possible and the best available correction been given, the patient is still unable to read 20/20 or shows other signs of poor vision, the visual acuity should again be carefully ascertained and recorded and an examina- tion made of the fundus for physical trouble. Carefully record all findings. The Visual Field. Whatever the ophthalmoscope may reveal, or even if it reveals nothing at all, the operator should proceed to ex- plore the visual field by means of the Perimeter or Campimeter, according to directions given above. The campimeter chart, when completed, should be attached to and form a part of the record. TRIAL CASE AND REFRACTIVE INSTRUMENTS 93 With the findings of the ophthalmoscope and the campimeter before him, the refractionist is in a fair posi- tion to continue to investigate any disease of the eye which may be present. It should be repeated here that the order of procedure above set forth is subject to variation according to the preference or experience of the individual operator. Many competent refractionists, for example, think it best to proceed at once to retinoscopy, after taking the vision, before employing the subjective tests. No doubt, in many cases this method shortens the time consumed in the entire examination and also has the advantage of fur- nishing certain guiding information. As stated, the author believes that these advantages are more than out- weighed by the tiring of the retina and by the complete picture of the case, from the patient's standpoint, which is obtained by the subjective tests just as in a medical case one always gains a more intelligent conception by exploring thoroughly all the subjective symptoms before proceeding to objective modes of diagnosis. In the last analysis, however, it is a matter for the individual oper- ators to determine for himself. Curren BOOKS Oculo -Refractive Cyclopedia and Dictionary By Thomas G. Atkinson, M. D. Complete, concise, sim- ple, profusely illustrated. Price, $5.00. Optical Shop Practice By W. W. Merritt. Thorough treatise on making of lenses, fully illustrated. Price, $2.00. Business Side of Optics By Roe Fulkerson. Invaluable to the practitioner de- siring to build up his clientele. Price, $1.00. Transpositions and Tables By Edward J. Lueck. Everything tabulated already for you. Price, $1.50. Text Boof^ of Iridiagnosis By J. Haskell Kritzer, M. D. Dealing with pathological and functional disorders of the human body indicated by abnormal lines, spots and discolorations the book you have wanted. Price, $5.00. Also Wall Chart of Iridiag- nosis (32 colored plates of the iris and enlarged "Iris", all in colors). Price, $2.50. Text Book and Chart, $7.00. The Profession; 17 No. Wabash Ave. literature BOOKS Muscles of the Eye By Geo. A. Rogers. Handling in a simple, comprehensive, masterful manner, ocular muscle functions and their anomalies that difficult question for practitioner as well as student. Fully illustrated. Price, $3.00. FOLDERS Interesting Facts Concerning Your Eyes One of the most popular folders ever used by the refractionists. An excellent business-puller. Per thou- sand, with your imprint, $7.50. New Wrinkles Another fine folder widely used. Shows that wrinkles frequently indicate need for glasses or else (for those already wearing glasses) different lenses. Per thousand, with your imprint, $6.00. CARDS Meissner Record Cards Standardize and systematize your practice. Used all over the United States. Per thousand, $4.00. Order from your jobber or ress, Inc. CHICAGO Oculo- Refractive Cyclopedia and Dictionary By THOMAS G. ATKINSON, M. D., B. Sc. A practical and comprehensive cyclopedia of ocular refraction and all the phases of op- tics, anatomy and physiology of the eye which relate thereto. Concise, clear, easy to consult. Plain in language, rich in illustration, graphic in pre- senting its subjects. Over 400 pages. Handsomely and Substan- tially Bound. Price $5.00 Net THE PROFESSIONAL PRESS, INC. 17 N. Wabash Avenue CHICAGO, ILL. JUL Form L9- u (2554)444 THE LIBRARY UNIVERSITY OF CALIFORNIA LOS ANGELES A 000 387 060 7