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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.
As many as 20% of Americans have been infected by the fungus known as Histoplasmosis. While most people are asymptomatic or only have slight symptoms, infection can progress to a rapid and potentially fatal superinfection.
The familiar sounds of your heart are made by the heart's valves as they open and close.
The first war in which wide-scale use of anesthetics occurred was the Civil War, and 80% of all wounds were in the extremities.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.