Eye anatomy, computer artwork. At the front of the eye is the cornea (grey), a transparent coating. Behind this is the lens (brown and pink), which is partly covered by the iris (blue). The lens and cornea focus light on the retina (orange) at the back of the eye. A magnified view of the retina is shown at upper right. Light sensitive cells (photoreceptors, red and brown) in the retina transmit signals to the brain via the optic nerve (grey, bottom right). Behind the rods and cones is a layer of pigmented epithelium that prevents light passing out of the eye, and behind that is the choroid, which contain blood vessels that nourish the back of the eye. The outer layer of the eye (white) is the sclera, the white of the eye.