428 THE HUMAN SPECIES 



turbances, former inflammation, haemorrhages into the anterior 

 chamber, or diabetes. The various operations for cataract are 

 also performed on animals. 



Glaucoma, which von Graefe showed was due to an abnormal 

 increase in intraocular tension, occurs, according to Moller, in 

 dogs and rabbits, though it is not common. It is characterised, 

 as in man, by the greenish hue of the retinal reflex and the 

 hardness of the eyeball ; the ophthalmoscope shows the same 

 hollowing of the optic disc. 



The condition known as amaurosis in animals is the result 

 of various diseases of the retina, optic nerve or visual centre in 

 the brain. 



Primary inflammation of the retina is seldom seen in 

 animals. In most cases it is secondary to choroiditis. Inflam- 

 mation at the point w r here the optic nerve enters the retina can 

 easily be recognised by the ophthalmoscope, as can separation 

 of the retina (dogs and horses), and haemorrhages, which are 

 frequent as the result of the infections, and of heart failure. 



Infectious diseases in horses and cattle also give rise to in- 

 flammation of the optic nerve before its entry into the medulla 

 (retrobulbar neuritis). 



Diseased conditions of the vitreous body are especially 

 common in horses, and are caused by disease of the choroid or 

 retina. The latter are usually due to wounds of the sclerotic, 

 and less often to inflammation. Dogs, lambs and cows are 

 predisposed to hydrophthalmos, in which the outer covering of 

 the eye extends through a complete sclerochoroidal staphyloma. 



The following conditions are similar to those seen in man, 

 and require similar treatment : inflammation of the lacrymal 

 sac (horses and cattle) ; closure or narrowing of the lacrymal 

 duct (horses, donkeys and mules) ; fistula (horses, cattle and 

 dogs) ; wounds and inflammation of the eyelids ; ectropia and 

 entropia (dogs). 



Swelling of the lids, ptosis and malignant or benign 

 tumours in animals have no special characteristics. 



The same lesions and inflammations of the soft parts of the 

 orbit may occur in horses and cattle as the result of work, and 

 in dogs as the result of fighting, and may occasionally result in 

 exophthalmos. 



