Eyesight
The Lens. The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. It is the second part of your eye, after the cornea, that helps to focus light and images on your retina. Your retina is in the very back of the eye. It holds millions of cells that are sensitive to light. The retina takes the light the eye receives and changes it into nerve signals so the brain can understand what the eye is seeing. Most of the eye is filled with a clear gel called the vitreous. Light projects through your pupil and lens to the back of the eye. The inside lining of the eye is covered by special light-sensing cells that are collectively called the retina. It converts light into electrical impulses. The eyeball houses the retina—an extremely metabolically active layer of nerve tissue made up of millions of light receptors (photoreceptors)—and all of the structures needed to focus light onto it. Working in concert with the aqueous humor behind it, the cornea provides the greatest focusing power of the eye.