The eye is like a camera with a lens in front and a film (retina) at the back. The cornea and lens in the front of the eye focus the rays of light onto the retina which then converts the image into electrical signals that are sent to the brain through the optic nerve.
The retina is a thin sheet of tissue which lines 2/3rds of the back of the eye. Fibers from all over the retina join to form the optic nerve which is in the center of the retina.