Vision is a person’s eyes and brain work together to see. The eye is made up of many different parts such as the cornea, iris, lens, and retina. These parts all work together to focus on light and images. The eyes then use special nerves to send what you see to your brain, so your brain can process and recognize what you're seeing. In eyes that work correctly, this process happens almost instantly. When any one of these body parts is damaged or does not function properly vision can be impaired and blindness can occur.

Blindness does not necessarily mean total darkness. Some individuals can see light, colors, and shadows. An individual can have some vision but still considered to be legally blind. Legally blind is determined as “visual acuity of 20/200 or worse in the better eye with corrective lenses (20/200 means that a person at 20 feet from an eye chart can see what a person with normal vision can see at 200 feet) or visual field restriction to 20 degrees diameter or less (tunnel vision) in the better eye.” according to Medicine.Net

There is also a difference between being legally blind and having total blindness. When someone has total blindness he/she will not have any vision, no ability to see light or shadows.

Medicine.Net. 2003. 10 August 2003. http://www.medterms.com/script/main/art.asp?articlekey=10614.