. Refraction and motility of the eye, with chapters on color blindness and the field of vision . eye tobe examined, from a plane mirror, while the movements ofthe reflex are studied by the physician through a centralaperture in the mirror. An electric retinoscope on thesame principle as the electric ophthalmoscope, but with aplane mirror, may be used. The position of the light maybe adjusted according to the preference of the observer,some having it placed on the level of and slightly behind theeye to be examined, while others place it a few inchesover the patients head. My preference is for t
. Refraction and motility of the eye, with chapters on color blindness and the field of vision . eye tobe examined, from a plane mirror, while the movements ofthe reflex are studied by the physician through a centralaperture in the mirror. An electric retinoscope on thesame principle as the electric ophthalmoscope, but with aplane mirror, may be used. The position of the light maybe adjusted according to the preference of the observer,some having it placed on the level of and slightly behind theeye to be examined, while others place it a few inchesover the patients head. My preference is for the last, butthe two chief requisites are that it shall be so placed that thelight may be reflected from the mirror into the eye with as(88) RETINOSCOPY. 89 little tilting of the mirror as possible, and that no lightshall reach the eve except that from the mirror, since thereflex or illumination of the retina will be much moredistinct against a dark background. The closer the lightis to the mirror the greater the intensity of illumination,but aside from this the distance of the light from the. Fig. 53. mirror is of no great importance, the only important dis-tance being that between the eyes of the observer andobserved. Neither is special apparatus for modifying orcondensing the light necessary, the only requisites being thatthe light be bright enough to illuminate the retina and yetnot so bright as to dazzle the patient. This can be securedwith an ordinary candle, if necessary, or regulated asdesired by the ordinary Argand gas burner or frostedincandescent bulb. If one always places the light on the 90 REFRACTION AND MOTILITY OF THE EYE. side and very close, an asbestos chimney is advantageousto modify the heat, and some of them are made withan iris diaphragm to modify the light if desired. Thesehave a certain advantage in that they do not light up thewhole dark room as does the uncovered light. The choice of a mirror is much more the work was originally done wi
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