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?
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
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The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
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Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
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Vaccines prevent between 2.5 and 4 million deaths every year.
