A cataract is a clouding of the lens in the eye that affects vision, making it blurry, cloudy or dim. Many people say that their vision with cataracts is like looking through a dirty car windshield.
A cataract can occur in either or both eyes. It cannot spread from one eye to the other. Most cataracts are related to aging and are very common in older people, affecting more than 50 percent seniors by the age 80. People can have an age-related cataracts in their 40s and 50s, usually small ones that do not affect vision. After age 60, most cataracts do impair vision.