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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.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
There are more sensory neurons in the tongue than in any other part of the body.
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.