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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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Vaccines prevent between 2.5 and 4 million deaths every year.
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In ancient Rome, many of the richer people in the population had lead-induced gout. The reason for this is unclear. Lead poisoning has also been linked to madness.
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It is difficult to obtain enough calcium without consuming milk or other dairy foods.
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Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.