What is a cataract?

A cataract is the clouding of the lens in the eye, which ultimately affects vision. The appearance of cataracts is usually an age-related occurrence, and most people begin to notice them by age 80. At this age, more than half of all North Americans will either have a cataract or have already had cataract surgery. A cataract can occur in either or both eyes but cannot spread from one eye to the other.