The choroid forms one of the layers that is part of the eyeball. It features an inner lining that ensures nutrition and adequate blood and oxygen supply to each individual part of the eye. The choroid is located between the sclera and the retina and consists of four stacked, layered components. The back side of the choroid is attached to the edges of the optic nerve and to the ciliary body from the front. The choroid is widely permeated by pigment which absorbs unnecessary light rays and prevents further dispersion into the eye.