The eye is the organ of sight in humans and animals. It transforms light waves into visual images and provides 80% of all information received by the human brain. These remarkable organs are almost spherical in shape and are housed in the orbital sockets in the skull. Sight begins when light waves enter the eye through the cornea (the transparent layer at the front of the eye), pass through the pupil (the opening in the center of the iris, the colored portion of the eye), then through a clear lens behind the iris. The lens focuses light onto the retina, which functions like the film in a camera. Photoreceptor neurons in retinas, called rods and cones, convert light energy into electrical impulses, which are then carried to the brain via the optic nerves. At the visual cortex in the occipital lobe of the cerebrum of the brain, the electrical...