THE EYE & SOME COMMON AFFECTIONS 221 



just as much as the exciting causes. It may be temporary 

 or permanent ; specific or non-specific ; and the degree of 

 bHndness varies with the position which the opacity 

 occupies, and also the time the trouble has been in exist- 

 ence. If the opacity has existed for a long time it gradu- 

 ally undergoes a hardening process, and nothing can ever 

 remove it.* Quite a common cause of this trouble is 

 striking the eye with a whip ; a blov/ over the eye with 

 the butt-end of the whip ; various irritants, etc. Horses 

 frequently shy at objects in the road when they have 

 slight opacity of the cornea, more particularly if the 

 cloudiness is directly over the pupil. 



Cataract 



This is a fairly common affection in horses and one 

 that may render a horse completely bhnd. It is a disease 

 affecting the crystalHne lens, the capsule covering the 

 lens, or both these structures. As a rule it is of gradual 

 onset, and once established it is permanent, as operations 

 on the horse for cataract are seldom performed. An 

 injury, such as a blow over the eye, may possibly be a 

 cause of cataract, but one of the commonest causes 

 during these last few years has been the so-called specific 

 or recurrent ophthalmia, a disease which produces so 

 much disorganisation within the eye and so frequently 

 recurs that structures in connection with the lens finally 

 become implicated, and cataract is the result. About 

 half a century since specific ophthalmia was in Gre'at 

 Britain a fairly common malady, and used to be known 

 under the title of moon bhndness. Since the Great War 

 recurrent ophthalmia has reappeared, principally among 

 the army horses, therefore it is reasonable to assume, 

 now that a large proportion of these animals have been 

 sold, that the trouble referred to will reappear some- 

 where. 



* Sclerosing keratitis. 



