Eye anatomy. Cutaway illustration passing through a human eye, showing its internal anatomy and structure. The front of the eye is at right, and the structures here include the cornea, the pupil (surrounded by the iris), and the lens (oval object). Light passes through these, and is focused on the retina (yellow), a layer of light-sensitive cells and blood vessels lining the inside of the eye. The light triggers signals that are passed through the optic nerve to the brain, where they are interpreted to provide vision. The inside of the eye is filled with a clear gel, the vitreous humour. At top and bottom are the eye muscles (muscles of the orbit, red).