Eye anatomy. Animation of the head showing a cutaway view of eye. Light entering the eye passes through the transparent cornea and then the pupil, a hole whose size is controlled by surrounded by the iris (brown). Behind this is the lens, which focuses light on the retina (light orange), a light-sensitive layer lining the rear and inside of the eye. The light triggers signals in the retina that are transmitted by the optic nerve (yellow) to the occipital lobe of brain (lit area at right). Behind the retina is the choroid (dark orange), which contains blood vessels that nourish the back of the eye. The outer layer is the sclera, the white of the eye. HD master is flattened onto a black background, as seen in this preview. The original file has a transparent alpha channel and is available as the HD master of clip number K003 3804.