426 DISEASES OF THE EYES 



especially in bulldogs, pugs and the toy spaniels, although it may occur 

 in any breed. The dog does not possess a complete bony arch of the 

 eye (zygomaticus), the space being filled up by a ligament, and the 

 muscles are also very weak. Occasionally, from some mechanical force, 

 such as blows in the region of the eye, or bites in its neighborhood 

 causing hemorrhage and a large amount of blood to collect in the posterior 

 part of the orbit, it is pushed out of position. Frec|uently the entire 

 eyeball is crowded out, standing out on the face clear of the orbit, (tumors, 

 etc.)- Simple pressure of the fingers on the supraorbital cavity of pugs 

 or spaniels is sufficient to make the eye protrude, opening the eyelids 

 mechanically; luxation of the inferior maxillary also causes protrusion 

 of the eyeball. It is also observed in that rare affection called Basedow's 



-tr-^i^ 



Fig. 149. — Dislocation of the eyeball. 



disease. This condition has been noticed in very rare instances to be 

 due to inflammatory processes inside the eye, and by the formation of 

 tumors in the orbits. 



The prognosis of a prolapsed eyeball depends largely upon the cir- 

 cumstances and condition of the organ. If the prolapse is of recent 

 origin, if the muscles of the eye and optic nerve are not torn, and if the 

 eye itself has not been very much injured, we may expect complete 

 recovery in a short time without any disturbance of sight. If the pro- 

 lapse is recent and the muscles are not torn, or only partially so, but the 

 eye is al)normally distended, we must expect there is some irritation of 

 the optic nerve, and while the eye may be restored the animal may 

 remain blind. If the muscles of the eye and optic nerve are lacerated 

 and the eye proper is injured, or if any of the chambers of the eye are 

 filled with blood, or if the prolapse has been sufficiently long that the 

 irritating influence of the air is marked by an opacity and a dry look of 



