How your eye sees Light entering the eye is focused by the cornea and the natural lens onto the retina, a thin, light-sensitive layer on the back wall of your eye. Portions of the retina which are stimulated by the light send electrical impulses to the brain via the optic nerve. The brain interprets these patterns of impulses to actually see what you are looking at. A cataract is a clouding or an opacity of the natural lens of the eye. This results in distortion of light rays as they pass through the lens, and a blurring of objects is seen.
Most cataracts develop as a result of normal aging and slowly become more dense.
Their rate of development varies greatly among individuals, with some people developing cataracts in their forties and others not until their eighties. Cataracts do not spread from eye to eye, but generally develop in both eyes. They usually progress at different rates, however, so vision in one eye is often better than in the other eye. A cataract is NOT a tumor or cancer of the eye. Some cataracts develop as a result of injuries to the eye, as a result of certain diseases, or due to hereditary conditions.