When you look at an object, light rays are reflected from the object to the cornea. The light rays are refracted and focused by the cornea, lens, and vitreous. The lens’ job is to make sure the rays come to a sharp focus on the retina. The resulting image on the retina is upside-down. There the light rays are converted to electrical impulses which are then transmitted through the optic nerve to the brain where the image is translated and perceived in an upright position.
The eye is somewhat like a camera which needs a lens and a film to produce an image. The eyeball needs a lens (cornea, crystalline lens, vitreous) to refract, or focus the light and a film (retina) on which to focus the rays. If any one or more of these components is not functioning correctly, the result is a poor picture. The retina represents the film in our camera. It captures the image and sends it to the brain to be developed. The macula is the highly sensitive area of the retina responsible for our critical focusing vision which we use to read.
