138 OPHTHALMOLOGY FOR VETERINARIANS 



the congenital type, and is due to faulty nutrition. A 

 senile cataract occurs late in life when the lens becomes 

 sclerosed, and is due also to faulty nutrition or to the 

 absorption of toxins from the circulation; and here a 

 toxic type might be mentioned, produced either by auto- 

 intoxication or the ingestion of toxic agents, such as the 

 ergot of rye, for example. Soft cataracts occur in the 

 young and hard cataracts in aged subjects. An incipient 

 cataract is one in its initial stage, before the vision has 

 become impaired, while a mature cataract is a lens which 

 has undergone complete change. This is also known as 

 a ''ripe" cataract, and is ready for extraction. A 

 primary cataract is one that appears without apparent 

 cause, while a secondary cataract follows disease of 

 other structures of the eye, such as glaucoma, etc. 

 Lenticular cataract is confined to the lens; it is also 

 known as cortical or nuclear, according to the location 

 of the opacity. When a cataract remains in the same 

 condition for a long period of time it is said to be sta- 

 tionary. The posterior polar cataract is classified 

 under this head, and also as congenital and capsular, 

 and its cause differs from that of other cataracts. A 

 progressive cataract is one that steadily advances to 

 maturity. Traumatic cataracts are the result of either 

 direct violence or accident during operations. 



As a rule, a cataract does not lessen the vision unless 

 it is centrally located. There is no inflammation present 

 that is dependent upon a cataract unless it is com- 



