DISEASES OF THE EYES. 271 



appearance may remain free from active disease for an indefinite 

 period. Then suddenly it is attacked again without any appre- 

 ciable cause. Each succeeding attack is marked by increased 

 severity, until loss of vision results. 



Treatment. — Treatment is unsatisfactory; the ailment cannot 

 be cured. The treatment can only be pallative, and is adopted 

 with the view of mitigating the severity of the attack. The treat- 

 ment should be similar to simple opthalmia. A purgative should 

 be administered — eight drachms of aloes. The disease termi- 

 nates in cataract. A cataract is an opacity of the crystalline lens, 

 or its capsule. It makes its appearance after subsidence of the 

 acute inflammatory stage of jieriodic opthalmia. It appears as a 

 little white sjieck in the center of the pupil. This grows at each 

 successive attack until it quite fills up the aperture. The vision 

 grows less and less distinct during its formation. Although 

 cataract is generally a sequel to periodical opthalmia, it by no 

 means follows that this is the only cause. It is occasionally no- 

 ticed in ground animals as soon as born, and is known as con- 

 genital cataract. It may result from an injury to the eye, or 

 without any previous irritation. 



Symptoms. — It can be easily detected, if it is of a good size. 

 The eye affected is retracted, sudden exposure to light causing 

 the eye to contract to an unnatural degree. To see a small cata- 

 ract, the horse should be placed in a darkened box, and the eye 

 examined with the aid of artificial light, as a candle. The pupil 

 should first be dilated with belladonna or atropine. The exam- 

 iner should keep any bright object, which he may have about his 

 person, concealed, or it may cause a reflection from the eye of the 

 patient and mislead the observer. On moving the light from 

 side to side there may be observed an erect image, which is re- 

 flected from the surface of the cornea. This image moves in the 

 same direction. A second image may also be seen, which is also 

 erect and moves in the same direction as the candle. This is 

 reflected from the anterior surface of the crystalline lense. A 

 third image, which is inverted and moved in the direction oppo- 



