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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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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
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Of the estimated 2 million heroin users in the United States, 600,000–800,000 are considered hardcore addicts. Heroin addiction is considered to be one of the hardest addictions to recover from.
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Cyanide works by making the human body unable to use oxygen.
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The first oncogene was discovered in 1970 and was termed SRC (pronounced "SARK").