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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.
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.
More than nineteen million Americans carry the factor V gene that causes blood clots, pulmonary embolism, and heart disease.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
In the United States, an estimated 50 million unnecessary antibiotics are prescribed for viral respiratory infections.