The eye is very complicated, but can be compared to a simple camera which has a lens at the front and photographic film at the back. In the eye there are essentially 2 lenses (cornea and lens) which focus the light on to the camera film (retina) lining the inside of the back of the eye. The information is then sent to the brain which "processes the photos" and produces a picture. When you are young the eye has an "auto-focus" mechanism and achieves this by changing the shape of the lens. As you get older, however, the autofocus mechanism breaks down and you are left with a fixed focus and need additional lenses to focus at different distances. These lenses commonly come in the form of reading glasses or "varifocals". The front part of the eye, between the cornea and lens is filled with a watery fluid called aqueous. The back part of the eye, between the lens and the retina is filled with a jelly-like substance called vitreous. The vitreous is attached to the retina at certain points. The white "outer wall" of the eye is called the sclera and is covered at the front by a transparent layer called the conjunctiva.
Cross section (sagittal) of eye. Courtesy, National Eye Institute, National Institutes of Health
Retina viewed from the front. Courtesy National Eye Institute, National Institutes of Health
www.retinalspecialist.com The Virtual Home of Niladri (Ted) Saha 2009