416 DISEASES OF THE EYES 



DISEASES OF THE CRYSTALLINE LENS. 

 Cataract. 



All diseases of the lens, either of its membranes or its capsule, as a 

 rule cause a certain amount of opacity, and may form one or more star- 

 like gray bodies in the centre of the lens itself (cataract). It is not 

 possible to enter into a description of the various forms of cataract 

 and its pathological alterations, but we will only take up one form (gray) 

 of cataract that can be subdivided into two forms — soft, which may 

 be congenital; or traumatic and hard or contracted cataract, which is 

 senile. The softening process generally begins in the equator of the 

 lens, and becoming diffused soon causes a total opacity of light gray 

 color. This may be streaked with darker lines or it may have a mother- 

 of-pearl discoloration, with enlargement or distortion of the lens and a 

 contraction of the anterior chamber. This is very often seen in young 

 animals. The contracting process, on the contrary, begins in the shape 

 of a number of small whitish striae, or dull opacities, in the peripheric 

 layers of the lenticular nucleus, and extend gradually over the cortical, 

 giving the lens a yellowish-white or yellow aspect after some time. 

 This is generahy observed in old dogs (hard nuclear cataract, senile 

 cataract). The so-called capsular cataract does not, as a rule, depend 

 on true opacity of the capsule, but on an accumulation of proilucts 

 of the same, which have been developed from disease processes which 

 have gone on in its immediate neighborhood. For instance, the in- 

 flammation of the iris. In some cases they appear in small, star-like 

 or streaked pigmented dull spots, which are distinctly marked. 



Etiology. — Gray cataract, as a rule, is a senile or old-age affection, 

 but it appears Ciuite frequently in young dogs; in this case the opacity 

 is deep-seated, and brilliantly white star-like opacities appear in the poste- 

 rior part of the lens, and now and then it is congenital. The writer saw one 

 case of hereditary star cataract in connection with microphthalmus. 

 Meleval observed in the progeny of a pair of poodles, where the dog had 

 a double cataract, that the pups had lenticular opacities. The develop- 

 ment of cataract which occurs in advanced age — that is to say, after 

 ten or twelve years — is what is known as senile cataract; this is slow in 

 its development, while cases of opacity of the lens, which are observed in 

 young animals, appear frequently without any marked cause, and run 

 their course very rapidly, the opacity forming in a few weeks, and even 

 in a few days the wliole lens has been completely covered. Traces of 

 sugar are found in the urine of dogs which become very thin and anaemic 

 in a short time, cataract frequently developing in this condition. Frohner 

 thinks that the lens becomes saturated with grape-sugar, which is present 



