The lens inside the human eye naturally undergoes compression, hardening, and certain chemical modifications. As these changes occur, the lens takes on a yellow or brownish hue and loses its clarity. Some degree of lens hardening and discoloration is normal as a person ages and may not interfere with visual function. Symptomatic cataracts are present when the levels of hardening and discoloration significantly degrade the original transparency and optical quality of the human lens.
Cataracts are very common in older adults.
While most cataracts develop in older adults they can occur in younger people, including newborns. Cataract formation depends upon several factors, and is not yet completely understood. Cataract formation occurring in otherwise healthy adults occurs as a result of compression and hardening of the center of the lens over time. This compression causes a breakdown in the lens proteins and decreases the transparency and clarity of the lens. Pediatric cataracts result from genetic and metabolic diseases, maternal infection, toxic or traumatic causes, as well as being hereditary.