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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.
According to the FDA, adverse drug events harmed or killed approximately 1,200,000 people in the United States in the year 2015.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.