CHAPTER VII. 

 DISEASES OF THE RETINA AND CHOROID. 



These membranes can be seen only with the ophthalmo- 

 scope. It is best to dilate the pupil in order to increase 

 the size of the field of the eye's background. 



The following pathological changes may be noted on the 

 retina: (a) Hyperemia, (6) edema, (c) inflammation (retin- 

 itis), (d) detachment of the retina, (e) anemia, (/) atrophy. 



Hyperemia. — A congestion of the retina. The blood- 

 vessels will be found dilated and engorged with blood. 



Edema.— Rare in animals. It may result from direct 

 injury, or inflammatory exudate which collects in the retina. 

 The retina appears cloudy. 



Inflammation {Retinitis). — An inflammation of the retina. 

 It usually develops during or as a sequel to infectious or 

 chronic constitutional diseases. It is characterized by hyper- 

 emia, edema, partial or complete obliteration of the papilla 

 and hemorrhage. 



Detachment of the Retina.— Have in animals. It may result 

 from an accumulation of exudate or transudate between 

 the retina and choroid, which causes the retina to become 

 detached and float loose in the vitreous humor. It causes 

 partial or complete blindness. 



Anemia.— Retinal anemia usually results from general 

 hemorrhage; obviously it accompanies general anemia. It 

 may have a local origin, the bloodvessels supplying the 

 retina becoming blocked and pressed upon by tumors or 

 inflammatory growths. The retina appears pale and the 

 bloodvessels reduced in size. 



Atrophy.— Usually follows extensive and severe retinitis; 

 or when the nutrition of the retina has become reduced. 

 The bloodvessels appear unusually small; in some cases 

 hardly visible. 



The diseases of the choroid are so intimately interwoven 

 with those of the other membranes that a separate descrip- 

 tion is unnecessary. 

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