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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.
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Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
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There are 20 feet of blood vessels in each square inch of human skin.
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The first oncogene was discovered in 1970 and was termed SRC (pronounced "SARK").
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The word drug comes from the Dutch word droog (meaning "dry"). For centuries, most drugs came from dried plants, hence the name.