A cataract is a clouding of the natural lens of the eye. The lens causes light rays to focus on the retina at the back of the eye, which in turn allows us to see. A healthy lens is transparent, but a cataract causes the lens to become cloudy, obstructing or hindering the passage of light.
Cataracts cause blurring and dimming of vision, as well as problems with glare.
It is important to recognize that a cataract is not a growth or a film over the eye. Cataracts are most commonly formed as a result of changes in the lens due to the normal aging process, although certain illnesses, chemicals, or an injury can also cause them to develop. Even if both eyes have a cataract, each cataract may develop at a different rate, causing vision to be worse in one eye. Depending on the type and placement of the cataract, a person could have a cataract and be unaware of it. Generally, however, if the cataract continues to develop, a person will notice gradual changes in vision, and eventually may be unable to see well enough to do the things they want or need to do.