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DISEASES OF THE EYE. 265 



almost impracticable, and is otherwise objectionable, inasmuch 

 as partial vision would alone be restored, which would probably 

 make the animal shy, as it is impossible to adapt spectacles to 

 him to supply the want of the lens, as is done in the human 

 subject. 



It often happens that when a cataract has completely formed 

 in one eye, the other, although it had been before attacked, 

 becomes strengthened and remains sound. This, indeed, is 

 the most favourable termination of specific ophthalmia that can 

 possibly occur. 



Partial cataract is the term applied to opaque spots in the lens, 

 when not sufficient to shut out vision entirely. It is generally 

 the consequence of active inflammation, which may recur again 

 and again until the transparency of the lens is entirely gone. 

 In other cases, the inflammatory attack may not again recur, but 

 partial vision remain through life. In examining a horse, we 

 may expect a recurrence of the inflammation if the other parts 

 of the eye are disorganised : but if the opacity is entirely con- 

 fined to the lens, and the other parts appear perfectly clear, 

 and the iris is not particularly irritable when exposed to the 

 light, we may consider it probable that the horse will preserve 

 Avhat sight he possesses, although, of course, he cannot be con- 

 sidered as sound. 



Sometimes we find slight specks on the crystalline lens 

 occurring without any previous inflammation, or at least any 

 that obtained notice. The appearance of these specks may, by 

 attention, be distinguished from partial cataract. Instead of 

 being white, yellow, or green, they are of a grey hue, and their 

 opacity is not so great as in cataract. It is extremely probable 

 that the opacity is confined to the capsule or covering of the 

 lens ; and, in several instances, I have known them disappear 

 without any remedy having been applied. Other veterinary 

 surgeons have made the same observations ; and it is now a 

 matter of doubt whether their existence is a cause of un- 

 soundness. — Ed.] 



Amaurosis, 



Or Gutta Serena, is blindness, either total or partial, from 

 supposed paralysis of the optic nerve. On inspecting the eyes, 

 we find no alteration of structure, but the pupil no longer 

 enlarges and diminishes from the eflfects of light, and the eyes 

 have an unusually bright or glassy appearance. The blind- 

 ness is sometimes total, at others partial ; sometimes it remains 

 incurable, at others it gives way to remedial measures. The 

 disease often comes on suddenly, and the first intimation received 

 is the horse's running against a wall or post. Amaurosis is of 

 several kinds ; it may depend on some lesion of the retina, and 



