DISEASES OF THE EYE AND ITS APPENDAGES 123 



When amaurosis has advanced so far that the animal is totally blind 

 it will generally be comparatively easy to form a correct diagnosis. The 

 dilated and immovable condition of the pupil, which is in no way affected 

 by a strong light, is in itself almost sufficient, but it also may be ascertained 

 in various other ways that the sight is lost. 



The manner in which the animal progresses is one of the most striking 

 indications of the existence of blindness. The fore-limbs are lifted un- 

 usually high, the head is elevated, the ears are constantly at attention, 

 and the gait is of the careful, dwelling kind. 



A common but not infallible test is that of riding the horse, c^uietly of 

 course, on to a wall, which he will touch with his nose before becoming 

 aware of its existence. This is a better method than that of making a 

 feint to strike the animal with a stick, because the motion which is given to 

 the air by the movement of the stick and the hand which holds it is often 

 sufficient to induce the horse to jerk the head away under the impression 

 that some foreign body is approaching him, thus leading the lookers-on to 

 suspect that a certain amount of visual power still exists. 



The great importance of the use of the ophthalmoscope for the examina- 

 tion of eyes which present any abnormal character, however slight, will be 

 understood when it is remembered that an animal with j^artial or even 

 complete amaurosis may be pa.ssed sound by a careless examiner. No treat- 

 ment is ever attempted for the cure of amaurosis in the lower animals. 

 Small doses of strychnia have been employed in the treatment of the 

 disease in the human subject with slight benefit, which has, however, 

 generally proved to be temporary. Galvanism has also been used, with 

 result of improving the sight for a short time, but neither of these remedies 

 has produced sufficiently good results to justify any recommendation of 

 them in the treatment of amaurosis in the horse. 



GLAUCOMA 



This disease is of very rare occurrence in the horse. It consists of 

 an increased tension within the eyeball in consequence of an excessive 

 secretion of the aqueous and vitreous humours. As a result of this the 

 eyeball is rendered full and unyielding to the touch, and somewhat 

 elongated from before to behind. By this change of form the animal 

 becomes myopic or short-sighted. One or both eyes may be affected, but 

 it is usually the case that the disease attacks each in succession, and 

 unless combated by treatment results in serious derangement of the in- 

 ternal structures, of which cataract is not an uncommon consequence. The 

 symptoms of glaucoma are variable, but it will be generally found that 



