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Did you know?
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
Did you know?
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
Did you know?
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
Did you know?
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Did you know?
Nearly 31 million adults in America have a total cholesterol level that is more than 240 mg per dL.