CHAPTER X 



DISEASES OF THE RETINA AND CHORIOID 



Diseases of these coats and also of the optic nerve 

 are diagnosed by the use of the ophthahnoscope. This 

 instrument is devised for throwing reflected light into 

 the eye from a tilting mirror in front of a series of spheric 

 lenses; a hole is in the center of the mirror, and the 

 small lenses are protected by a circular revolving disk. 

 Two methods of examination are used: The direct 

 method, by which the physician looks directly through 

 the hole in the mirror, the same being close to the 

 animal's eye. The light (a candle is sufficient) is placed 

 to the right of the animal's head if the right eye is to 

 be examined, the ophthalmoscope being held in the right 

 hand, and the examiner uses his right eye. In examining 

 the left eye, hold the instrument in the left hand, and 

 look through the hole in the mirror with the left eye. 

 The-' light should be on the left side of the animal's 

 head. When examining either eye the mirror is brought 

 close to the eye of the animal, and so tilted as to produce 

 a red reflex, when the fundus will be illuminated. If 

 the vessels are seen, but are indistinct, the disk may be 

 turned so as to bring out the vessels sharply by either 



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