418 



DISEASES OF THE EYES 



action of the lens in the eye itself. Before doing so, however, we must 

 dilate the pupil with atropia. 



Discoloration of the lens may be caused by violent concussion, con- 

 tusion of the eyeball, and by various pathological conditions in the 

 interior of the eye. It may be congenital, the lens being in a variety of 

 positions in the eye, sometimes it is necessary to dilate the pupil by 

 means of atropine to ascertain the exact position of the lens. 



The prognosis is rather difficult to make, and, as a rule, it should 

 be an unfavorable one. Hereditary cataract shows little inclination to 

 enlargement, as is also the case in senile cataract. In soft cortical cata- 

 racts seen in young animals, we may see a rapid opacity of the lens in a 

 few days or weeks. The sight is entirely lost and medical treatment 

 is of little use. 



Therapeutic Treatment. — In the early stages of senile cataract very 

 good results have been obtained with iodide of potassium, 1 per cent. 



Fig. 143. — a. Stop discission needle; b, Graefe's cataract loiife; c, DavieFs cataract spoon. 



solution, few drops in the eye daily. A gray cataract may be removed 

 by an operation, and this is much more advisable in the dog because 

 it is, as a rule, particularly in young dogs, attended with no great 

 danger, and its results are generally beneficial, producing a partial res- 

 toration of the vision. It is advisable to perform the operation of 

 cataract after having first dilated the pupil by means of atropia, and 

 then performing the operation under ether. The writer has tried 

 cocaine alone, but he finds it unsatisfactory. The animal must be 

 tied up, placed on a table, and ether or chloroform administered. The 

 operation is performed by one of the following methods: 



Opening of the Capsule. — The anterior capsule of the lens has to be 

 opened in a transverse way with what is known as a discission needle 



