134 OPHTHALMOLOGY FOR VETERINARIANS 



tortuous. The disk appears ' 'choked/' and the tissues 

 have a striated appearance from the center outward, 

 extending into the retina. Vision may be normal in 

 some cases, though a marked decrease in the fields and 

 acuity of vision is the rule, and sudden blindness some- 

 times occurs. The prognosis is always grave. 



Retrobulbar neuritis is inflammation of the nerve 

 within the orbit, posterior to the globe. It is often caused 

 by influenza and catarrhal disturbances of the nasal 

 passages, involving the sinuses directly adjacent to the 

 orbital tissues. It may occur in one or both nerves. 

 Total blindness may follow an acute attack, caused by 

 severe inflammation of the orbital tissues, though 

 in the majority of cases only a varying decrease in the 

 visual acuity is the result. The fundus is normal in 

 appearance, though atrophy of the nerve-fibers may take 

 place and descend to the papilla, when it will gradually 

 become white. The prognosis is usually good if the 

 cause is removed and the nerve-fibers toned by proper 

 medication. 



Toxic amblyopia is due to poisons within the system. 

 In man, alcohol and tobacco are the principal causes, 

 though lead, arsenic, and various other chemic poisons 

 may be the cause. Quinin in large doses has produced it. 

 ^'Anatomic investigations in quinin-poisoning, produced 

 experimentally in dogs, shows during the very first 

 days a destruction of the ganglion cells of the retina, 

 these being primarily attacked by the poison" (Duane). 



