The eye allows us to see and interpret the shapes, colors, and dimensions of objects in the world by processing the light they reflect or emit. The eye is able to see in bright light or in dim light, but it cannot see objects when light is absent.
Process of Vision
Light waves from an object enter the eye first through the clear cornea and then through the pupil, the circular aperture (opening) in the iris. The light waves are converged first by the cornea, and then further by the crystalline lens, to a nodal point located immediately behind the back surface of the lens. At that point, the image becomes inverted.
The light progresses through the gelatinous vitreous humor and, ideally, 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. Actually, then, we do not “see” with our eyes but, rather, with our brains; our eyes merely assist with the visual process.