Cataract. Opacity of the Lens or Its Capsule. 433 



the animal may be taken into a dark chamber and examined 

 by one of the following methods : 



A light, preferably a candle, is placed in front of the eye and 

 moved from side to side, upward and downward, so as to bring 

 its images over all parts of the cornea and lens. In the normal 

 eye there are reflected three images of the light, one large, clear, 

 and upright from the anterior surface of the cornea, one, much 

 smaller but still upright, from the anterior capsule of the lens, 

 and one, small and inverted, from the posterior surface of the 

 lens and capsule. Any opacity in the lens or on its posterior 

 capsule, will cause the posterior (inverted) image to become in- 

 distinct, and as it were a diffuse white blur, as it passes over that 

 spot. The other small (erect) image may be even clearer than 

 normal in passing over the opaque area because of the mirror-like 

 reflecting action of the white cloud behind it. The movement of 

 the light so as to pass its. image over all parts of its surface in 

 succession will certainly reveal the existence and seat of the cata- 

 ract, by the blurring of the inverted image of the flame. 



Another method is by oblique illumination, the patient's head 

 being turned away from the light and the interior of the eye 

 being lighted up by reflection from a mirror. If the pupil has 

 been sufficiently dilated all parts of the lens can be scrutinized 

 in this way and the slightest opacity detected by the grayish or 

 whitish haze. 



If there is still doubt as to the nature of such appearances, it 

 may be set at rest by illuminating the depth of the eye with the 

 ophthalmoscope when the opacities will appear as dark areas in 

 the general red ground. See Systematic Examination of the 

 Eye.) 



The prognosis of cataract is almost invariably hopeless. I 

 have seen newly formed opacities of the capsule clear up in a day 

 or two, and such recovery in very slight traumatic injury and 

 superficial exudation is recognized as possible, but a slowly form- 

 ing cataract is usually there to stay. Those that clear are pre- 

 sumably only exudates on the capsule and not true cataracts. 



Treatment. While exudates on the capsule may disappear 

 under a course of purgatives and diuretics, practically nothing is 

 to be expected from medical treatment in true cataract. The in- 

 stillation of phosphorated oil (i - 2 percent.) daily into the con- 

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