External and Internal Eye Anatomy

The cornea allows light to enter the eye. As light passes through the eye, the iris changes shape by expanding and letting more light through. Or, it constricts and lets less light through to change the size of the pupil. The lens then changes shape to allow the accurate focusing of light on the retina. Photoreceptors in the eye transmit nerve signals through the optic nerve to the brain. The brain processes these nerve impulses into sight.