126 OPHTHALMOLOGY FOR VETERINARIANS 



with the addition of a spheric lens of about +i6 

 diopters. In using this method the disk should be 

 turned so that a +3 D. lens shows behind the hole in 

 the mirror. Support the 16 D. lens with the thumb and 

 index-finger of the right hand (for the left eye, and with 

 those of the left hand for the right eye) , and allow the 

 Httle finger to rest upon the face near the eye, so as to 

 guide the distance between the eye and the lens. The 

 examiner will hold the ophthalmoscope close to his own 

 eye, and pass the reflected light through the 16 D. lens 

 near the animal's eye. This method gives a greater 

 field, but a reduced image, and usually brings out the 

 retinal vessels and optic disk distinctly, even in cases 

 of a high myopia. 



It will be well for the veterinary student to use the 

 ophthalmoscope as much as possible in the examination 

 of the eyes of various animals, and become acquainted 

 with normal fundi. This is the only possible way to be 

 able to distinguish a normal from a diseased fundus. 

 Examine the human eye also, and study the difference 

 in the structure of the coats and the arrangement of the 

 vessels from those of dumb animals' eyes. (See Frontis- 

 piece.) 



Normal fundi of animals of a kind are the same, 

 though they may differ in degree of shade or color 

 according to the amount of pigment. Anomalous con- 

 ditions (such as coloboma of the chorioid or retina) may 

 be mistaken for a pathologic change, but experience in 



