CHAPTER VIII. 

 DISEASES OF THE OPTIC NERVE. 



Usually when the optic nerve is affected diseases of 

 other structures, particularly of the retina, co-exist. 



The principal pathological changes affecting the optic 

 nerve are: (a) Wounds, (b) hemorrhages, (c) inflammation, 

 (d) tumors. . 



The optic nerve is also affected by inflammation of adja- 

 cent structures, and diseases of the central nervous system: 



The diseases of the optic nerve usually noted are: (a) 

 Papillitis, (b) retrobulbar neuritis, (c) atrophy. Clinically 

 amblyopia and amaurosis are recognized. 



PAPILLITIS. 



Definition.— An inflammation of the papilla. It may be 

 unilateral or bilateral. It is usually caused by poisons, 

 traumatism and diseases of the central nervous system. 

 Viewed with the ophthalmoscope the papilla appears either 

 enlarged and engorged with blood or, on the other hand, too 

 pale— even white in color. Its outline is usually indistinct 

 and striations are seen radiating from its center. When 

 due to tumors and marked congestion is present, the papilla 

 appears intensely red ("choked disk"). 



Prognqsis. — The prognosis is unfavorable. Partial or com- 

 plete blindness will usually result. 



RETROBULBAR NEURITIS. 



Definition.— An inflammation of the optic nerve just 

 posterior to its entrance into the eyeball. It may result 

 from injuries, infection through wounds involving the 

 orbit; or attend nasal catarrh, or dog distemper which has 



