The lens is a very important part of the eye for focusing light. In the normal eye, the lens is a flexible bag of protein which, in young people, is crystal clear. The lens has the ability either to flatten or to thicken, thereby bringing objects into focus. A cataract is not a growth or cancer, and it is not the same as glaucoma. All cataracts form in the same place - in the lens of the eye.
Cataracts are a leading cause of blindness.
They can be present at birth, caused by diseases such as diabetes mellitus, or be due to injury. However, about ninety percent of all cataracts form as a result of the aging of the lens which can occur as early as age 40. Although cataracts can develop in people at any age, it is certain that people who live long lives will eventually develop cataracts. Once a cataract develops, it will continue to grow. Most cataracts grow slowly over a period of years, though some develop more rapidly.