540 DISEASES OF THE IRIS AND CILIARY BODY 



MYDRIASIS. 



Definition. A dilatation of the pupil. It may be due to: 

 (a) Paralysis of the third nerve, (6) disease of the central 

 nervous system, (c) constitutional diseases, (rf) poisons, (e) 

 mydriatics. 



Mydriasis is produced artificially in order to examine 

 the interior of the eye. 



MYOSIS. 



Definition. A contraction of the pupil. It is caused by 

 paralysis of the cervical sympathetic nerves, tabes dorsalis, 

 inflammation of the iris, foreign bodies in the cornea and by 

 myotic drugs (morphin, codrenin, eserin). It is frequently 

 noted in rabkr"animals. 



IRITIS AND CYCLITIS. IRIDOCYCLITIS. 



Definition. An inflammation of the iris and of the ciliary 

 body. They usually co-exist and will be therefore con- 

 sidered together (iridocyclitis). 



Etiology. Traumatism. A primary iridocyclitis is not 

 common. Most cases are secondary to other diseases, 

 such as distemper of the dog and cat. 



Symptoms. Iridocyclitis is characterized by congestion, 

 discoloration, loss of the normal striations and inability 

 of the iris to react to light or other stimulae. The pupil is 

 usually found contracted. While it is possible for the 

 iridian exudate to be very limited, the inflammation stopping 

 in the congestive stage, as a rule, it is profuse, falls off 

 the iris and accumulates in the anterior chamber (hypopyon 

 if purulent). The exudate, which is usually fibrinous, may 

 be seen through the cornea as a movable, yellow, sometimes 

 blood-streaked accumulation floating in the anterior cham- 

 ber. If an adhesion between the iris and the cornea results, 

 anterior synechia is spoken of; if between the iris and lens, 

 posterior synechia. Symptoms of lacrimation, photophobia 

 and congestion of the conjunctiva are usually present. The 

 cornea is nearly always involved, appearing as if lightly 

 greased over its surface. When the ciliary bodies are 



