Cataracts Health Center

A cataract is clouding of the lens inside of the eye to an extent that affects vision. The lens is the clear part of the eye located behind the pupil, which is used to focus light upon the retina. In a healthy human eye, light passes through this transparent lens to reach the retina, which then changes this light into nerve signals sent to the brain. For the retina to receive and translate light or an image, the lens must be clear. If the lens is cloudy due to a cataract, the image received in the brain will be blurred. 

Most cataracts are the result of aging and thus are very common in elderly individuals. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. Cataracts are not limited to a particular eye — they can occur in either or both eyes simultaneously. The condition cannot spread from one to the next. 

There are many types of cataracts, but most are related to aging. Other types of cataracts include:

  • Secondary cataract: Secondary cataracts can form after surgery or from other eye conditions such as glaucoma. These cataracts can also develop in people who are battling other health issues like diabetes. 
  • Traumatic cataract: Some eye injuries can lead to a higher risk for later development of cataract, which can occur even years after the initial incident. 
  • Congenital cataract: Small cataracts, which affect newborns and young children, may develop in both eyes. However, these cataracts might be so tiny that they do not negatively impact vision. Although in some cases, the lenses may need to be removed if vision is severely affected. 
  • Radiation cataract: Exposure to radiation can sometimes cause cataracts and trauma to the eyes.
Review Date: 
July 11, 2012
Last Updated:
January 15, 2014