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A cataract is a clouding of the lens of the eye that can impair vision. More than half of all Americans age 65 and older have cataracts.

What Causes Cataracts?

The eye functions much like a camera. Light rays enter the eye, passing through the cornea, the aqueous humor -- transparent fluid in the front of the eye -- and then the pupil and into the lens. The lens bends the light rays to focus objects onto the retina lining the back of the eye. From there, the image passes through the retinal cells, into the optic nerve, and finally to the back of the brain which process the images.

Cataracts occur when there is a buildup of protein in the lens that makes it cloudy. This prevents light from passing clearly through the lens, causing some loss of vision. Since new lens cells form on the outside of the lens, all the older cells are compacted into the center of the lens resulting in the cataract.

Types of cataracts include:

  • Age-related cataracts. As the name suggests, this type of cataract develops as a result of aging.
  • Congenital cataracts. Babies are sometimes born with cataracts as a result of an infection, injury, or poor development before they were born, or they may develop during childhood.
  • Secondary cataracts. These develop as a result of other medical conditions, like diabetes, or exposure to toxic substances, certain drugs (such as corticosteroids or diuretics), ultraviolet light, or radiation.
  • Traumatic cataracts. These form after injury to the eye.

Other factors that can increase a person's risk of developing cataracts include cigarette smoke, air pollution, and heavy alcohol consumption

Cataracts Eyes

What Are the Symptoms of Cataracts?

Cataracts usually form slowly and cause few symptoms until they noticeably block light. When symptoms are present, they can include:

  • Vision that is cloudy, blurry, foggy, or filmy
  • Progressive nearsightedness in older people often called "second sight" because they may no longer need reading glasses.
  • Changes in the way you see color because the discolored lens acts as a filter.
  • Problems driving at night such as glare from oncoming headlights.
  • Problems with glare during the day.
  • Double vision (like a superimposed image).
  • Sudden changes in glasses prescription.