A cataract occurs when the lens of the eye becomes clouded by protein deposits. The clouding causes a decline in clear vision.
There are three types of cataracts. They include subcapsular cataracts, nuclear cataracts, and cortical cataracts. Subcapsular cataracts develop at the back of the lens. Nuclear cataracts appear in the center or nucleus of the lens. A cortical cataract begins around the edges of the lens and encroaches upon the center of the eye.