SEC. 11. THE NUTRITION OF THE EYE. 



603. The main blood-vessels of the eye are, the arteria 

 cen trails supplying the retina, and the (posterior) ciliary arteries 

 supplying the choroid, ciliary processes and iris, the vessels 

 going to the choroid being called the short ciliary arteries, and 

 those reaching forward to the ciliary processes and iris, the long 

 ciliary arteries. From the arteria centralis retinae the blood is 

 returned by the vena centralis, while the vense vorticosse of the 

 (posterior) ciliary veins gather up the blood of both the long 

 and the short (posterior) ciliary arteries. These two systems 

 communicate to some extent with each other by anastomoses 

 at the entrance of the optic nerve, but on the whole are inde- 

 pendent. 



In addition to the above, the anterior ciliary arteries pass to 

 the eyeball with each of the four straight ocular muscles, sup- 

 plying the front part of the sclerotic as well as the edge of the 

 cornea, and sending through the sclerotic 4 perforating ' arteries 

 to end in the iris, ciliary processes, and front part of the cho- 

 roid, and so join the system of the posterior ciliary arteries. 

 Corresponding to these anterior ciliary arteries 'are veins which 

 make their way back to the ocular muscles, and the roots 

 of which are especially connected with the circular canal of 

 Schlemm. Further, the edge of the cornea is in addition 

 supplied by conjunctival blood-vessels. 



The blood-supply of the various parts of the eye is therefore 

 somewhat as- follows. The inner layers of the retina are sup- 

 plied in a direct manner by the arteria centralis retinae, but the 

 outer layers together with the pigment epithelium in an indirect 

 manner by the close set choroidal network " choriocapillaris " 

 of the posterior ciliary arteries. The choroid proper, that part 

 which serves as an investment to the retina and specialized 

 pigment epithelium, is supplied by the short (posterior) ciliary 

 arteries ; but the front ciliary part of the choroid, together with 

 the ciliary processes and iris, receives blood from the long (pos- 

 terior) ciliary arteries, and also from the anterior ciliary arteries. 

 The cornea is supplied by the conjunctival as well as by the 



969 



