Choroid

The choroid is the vascular layer of the eyeball. It lies between the retina and the sclera. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.

The structure of the choroid is divided into four layers: 1) Haller's layer, which is the outermost layer of the choroid consisting of larger diameter blood vessels; 2) Sattler's layer, layer of medium diameter blood vessels; 3) Choriocapillaris, which consists of a layer of capillaries; 4) Bruch's membrane, the innermost layer of the choroid.