]12 THE PRACTICE OF VETERINARY MEDICINE. 



be sufficient to cause complete loss of vision. Complete or 

 partial loss of vision, as the termination of periodic ophthal- 

 mia, is in every case but a question of time. It is claimed 

 that Lexington, one of the greatest racehorses and sires 

 America ever produced, went blind from severe exertion ; 

 but there can be no reasonable doubt that the trouble 

 was periodic ophthalmia, simply developed by exertion. 

 It is a significant fact in proof of this, and also that it is an 

 hereditary trouble, that a large number of the progeny of 

 Lexington became blind. 



Symptoms. — A peculiarity of periodic ophthalmia is the 

 suddenness of the attack. The groom reports that he left 

 the horse at night all right ; in the morning he found one 

 or both eyes swollen, sore, etc. (as a rule, but one eye is 

 aff'ected at a time), and he supposes the horse has a cold in 

 his eye, or has ^ot a hay-seed or some other foreign sub- 

 stance in it. The eye is intolerant of light, and is retracted 

 within its socket, and on this account appears smaller than 

 its fellow. There is a drooping of the eyelid, and a slightly 

 reddened condition of the conjunctiva, but not nearly to 

 such an extent as in simple ophthalmia. The cornea is dim 

 n appearance, with a well-marked ring around it. Another 

 sign is the unnatural contraction of the pupil, very well 

 marked on exposing the eye to light. As the disease ad- 

 vances, the interior of the eye loses its brilliancy and trans- 

 parency, and presents a sort of yellowish-brown appearance, 

 which is hard to describe, but once seen will always after- 

 wards be easily recognised. This appearance is caused by 

 the exudate which has been thrown out. The iris is always 

 affected to a degree depending on the severity of the inflam- 

 mation. A purulent discharge from the eye, more or less abun- 

 dant, takes place. The iris may adhere to the crystalline lens, 

 after which atrophy of the eyeball begins. As the disease 

 progresses, the eye clears up somewhat, and the exudate, 



