Ultraviolet (UV) radiation, such as sunlight, is absorbed by the lens of the eye and can lead to the formation of chemicals called free radicals inside the lens. Over time, free radicals may damage the lens, causing cataracts.

People exposed to excessive amounts of sunlight because of their profession (such as agricultural workers), geographic area (such as the southwest and other sunny parts of the United States), or use of tanning booths or sunlamps may be more likely to form cataracts.

It is not known for certain whether reducing UV exposure helps prevent cataracts.