41 



is designated lenticular cataract. Lentiular cataract may be 

 partial or complete; the former when a small portion of the 

 lens substance is involved and the latter when the 

 entire lens becomes opaque. The causes of cataract are 

 various; and in some cases are not distinctly understood. 

 Occasionally a cataract may be present in one or both eyes 



Fig. 11. 

 Partial Cataract (after Armatage). — The opaque spot or spots in 

 the lens or its capsule may be seen through the pupillary opening. 

 Spots in the cornea should not be mistai^en for the deeply located 

 opacities in the lens. 



at birth. Heredity, no doubt, exercises a great influence in 

 the production of cataracts during foetal life and also pre- 

 disposes an offspring to the disease in later life. Cataract 

 frequently manifests itself in the course of diabetes mellitis 

 (sugar in the urine) but there is no positive proof that the 

 sugar in the system causes the cataract. Hemorrhages 

 (bleeding) in the aqueous chamber lead to straining of the 

 capsule; the coloring matter of the blood is deposited in the 

 capsule and the dark colored opacity remains after the blood 

 is absorbed or removed from the aqueous chamber. Dis- 

 turbances in the nutrition of the lens in old age is said to be 

 the cause of senile cataract. In old age the lens substance 

 becomes more and more solid ; this leads to irregularity in 

 its density ; also prevents changes in the curvature of the 

 lens that are necessary in the adjustment, or its accommoda- 

 tion, to different distances. The constant straining of the 

 eye to bring a hardened lens to the various positions or forms 



