The Human Eye (image) American Chemical Society Share Print E-Mail Caption A cataract is a clouding of the lens in the eye that affects vision. Most cataracts occur in older persons. By age 80, more than half of all people in the United States either have a cataract or have had cataract surgery. Credit (Courtesy of NIH/National Eye Institute) Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.