igo OPHTHALMOLOGY FOR VETERINARIANS 



sponds; but in older subjects it loses its elastic qualities 

 and responds less readily to the action of the ciliary mus- 

 cle, and objects which could formerly be seen near the 

 eye have to be carried much farther away to be seen 

 distinctly. This is noticeable in man at about forty- 

 five years of age, and spheric lenses have to be placed 

 before the eyes to make up the deficiency. The condi- 

 tion is known as presbyopia. 



Accommodation is usually determined between two 

 points, known as the near point (punctum proximum) 

 and the far point (punctum remotum). The near point 

 is that point nearest the eye at which a certain object 

 can be seen distinctly. The far point is the greatest 

 distance from the eye at which the same object can be 

 distinctly seen. These points vary with different in- 

 dividuals, and especially so when errors of refraction 

 exist. 



The hyperopic eye will necessarily have to accommo- 

 date proportionately more than normal, and the myopic 

 eye less so or not at all. This is because, in the first 

 instance, the focus is back of the retina when the. ac- 

 commodation is at rest; and, in the second instance, it 

 is anterior to the retina. In hyperopic eyes the ciliary 

 muscle is overdeveloped, while in myopic eyes it is often 

 atrophied from non-use. 



During accommodation the eyes converge propor- 

 tionately to the distance, and the pupil is diminished in 

 size, reflexly. The pupil is dilated when the muscle of 



