Home Page
Consumers' Section

E-mail this page   Printable View

Cataracts: Overview and Risk Factors

Cataracts are extremely common. They affect an estimated 15 million people and are responsible for nearly half of all cases of blindness worldwide.

A cataract occurs when the lens of the eye becomes cloudy or opaque. This happens gradually, as proteins in the lens become oxidized. Doctors do not know exactly why this occurs, but they believe that a combination of environmental factors (such as toxins and sunlight exposure) and genetic factors are involved.

Cataracts can occur in specific areas or throughout the lens. The process usually occurs very slowly over the course of years or decades, and it usually affects both eyes.

Cataracts are not painful. The most common symptoms are loss of vision, blurred vision, or double vision. In general, long–distance vision is lost before near vision. Some patients say that they see a halo effect around lights. Others note excessive glare during night driving and in bright light, especially sunlight.

Risk Factors

Although the exact cause of cataracts is unknown, there are several factors that increase risk of cataract formation. These include:

  • Smoking: Doctors believe that at least 20 percent of cataracts in the U.S. occur due to cigarette smoking.
  • Increasing age: Most cataracts occur in individuals over 60.
  • Family history of cataracts
  • Diabetes mellitus
  • High cholesterol
  • Obesity
  • Excessive alcohol use
  • Excessive sunlight exposure


Cataracts: Diagnosis and Treatment >>