Light from an object enters the eye first through the cornea and then through the pupil, the circular opening in the iris. Next, the light is converged by the lens to a point immediately behind the lens; at that point, the image becomes inverted. The light progresses through the gelatinous vitreous humor and back to a clear focus on the retina, the central area of which is the macula. In the retina, light impulses are changed into electrical signals and then sent along the optic nerve and back to the occipital (posterior) lobe of the brain, which interprets these electrical signals as visual images.

In a normal eye, rays of light from an object are focused at a sharp point on the Retina.