Adapted from the National Eye Institute, U.S. National Institutes of Health. Available online: http://www.nei.nih.gov

The retina is a thin nerve membrane that detects light entering the eye. The light causes nerve cells in the retina to send signals along the optic nerve to the brain. The brain interprets the signals as a picture of what the eye saw.

The retina lines the back two-thirds of the eye. The macula, near the center of the retina at the back of the eyeball, provides the sharp, detailed, central vision a person uses for focusing on what is directly in the line of sight.

The rest of the retina provides side (peripheral) vision, which lets a person see shapes but not fine details. The optic disc is the point inside the eye where the nerve that leads from the eye to the brain (optic nerve) leaves the eye.