Essay by Gena_High School, 11th grade November 2005

download word file, 12 pages 5.0

Did you see blind people? I think you did. Did you think how they live? Do you know what problems they have? While I made this investigation I understood much more about blindness. This is a result of my investigation.

What causes blindness?

The eye and a camera have a lot in common. They both have compound lenses. The cornea and the lens are in charge of focusing light as it enters the eye. The lens is adjustable to allow viewing of both close and distant objects. The iris, just like the iris in a camera, controls the amount of light that enters the eye. It opens and closes to protect the sensitive retina from to much light. The retina covers the back of the eye. It contains millions of photo-receptor cells. These cells react to the presence and intensity of light and send impulses to the brain through the optic nerve.

These impulses are converted into sight by the brain.

There are many things, which cause blindness. Sometimes people are born blind, their blindness or visual impairment is congenital (meaning "born with"). But most blind people become blind later on. Some people become blind after accidents. Wearing protective eyeglasses or goggles during activities such as using power tools, playing racquetball, or working with chemicals can help prevent such accidents. Glaucoma, cataracts, and diabetic retinopathy are the three most common causes of blindness today.

Glaucoma is a disease that causes increased fluid pressure inside the eye. A fluid called the aqueous humor fills the gap between the lens and cornea. There are valves in this part of the eye that regulate the eye's internal pressure. The increased pressure, from this condition, destroys the optic nerve. It can cause blindness and also tunnel vision. If you close one eye and look...