A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
For all of the NEI information on this topic, please visit the following webpage:
Facts About Cataracts
For more information from other health sites, please visit the following webpages:
Medline Plus, Cataract
University of Maryland Medical Center, Cataracts