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What Are Cataracts?

By , Caring.com senior contributing editor
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Cataract basics

Cataracts develop naturally over time. In fact, more than half of Americans age 80 or older either have a cataract or have had cataract surgery. Except in the most developed countries, cataracts are the leading cause of blindness worldwide. If someone has a cataract, it means he has a cloudy area on the lens of his eye. How will cataracts affect a person's vision, and how can you help him cope?

The good news about cataracts

With surgery, they can be reversible.

What happens with cataracts

A cataract is a clouding of the eye's lens. Light passes through the lens (located behind the iris and the pupil) to the retina, which sends an image to the brain. If the lens isn't clear, the image reaching the retina will be blurry.

This clouding happens over time. The eye's lens is made up of protein and water, and when protein cells break down and clump together on the lens they form a cataract, causing blurred vision. If the cataract gets larger, it clouds more of the lens, making vision increasingly difficult. The lens may also become thicker and more rigid, and it may change from clear to a yellow-brown that tints what a person sees.

Cataracts are classified according to where they occur in the lens, and the type affects the symptoms a person will experience.

  • If he has a nuclear cataract, for example, it's forming in the center of the lens.
  • A subcapsular cataract appears at the back of the lens.
  • A cortical cataract occurs on the edges of the lens (but eventually sends streaks to the center of the lens).

Vision loss from age-related cataracts is most common in people over age 60, though age-related cataracts can form much earlier. Some experts think the lens changes over time because of free radicals (from smoking and ultraviolet light, for example) as well as from general wear on the protein fibers.

A person may have a cataract in one or both eyes, though it's most likely that he'll develop cataracts in both eyes.