Harvard Women's Health Watch

By the way, doctor: What can I do to prevent cataracts?

Q. Is it true that cataracts are made of calcium? Can I do anything to avoid getting a cataract? What about diet?

A. A cataract is a vision-clouding area in the lens of the eye. About half of all people ages 65 to 74, and 70% of those ages 75 and over, develop cataracts, which are the leading cause of blindness worldwide. Fortunately, surgery is safe and effective; in places like the United States, where it's one of the most common operations performed, it leads to improved vision in about 90% of cases.

Cataracts aren't made of calcium but rather of clumps of protein. Normally, the lens of the eye works like a camera lens to focus light on the retina at the back of the eye (see illustration) and to adjust the eye's focus, which allows us to see things clearly at varying distances. The cells of the lens are composed of water and protein arranged in a way that keeps the lens clear. For reasons that aren't fully understood, the protein molecules may clump together and start to cloud the lens. This is the beginning of a cataract. The effect has been likened to cooking an egg white.

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