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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.
Hypertension is a silent killer because it is deadly and has no significant early symptoms. The danger from hypertension is the extra load on the heart, which can lead to hypertensive heart disease and kidney damage. This occurs without any major symptoms until the high blood pressure becomes extreme. Regular blood pressure checks are an important method of catching hypertension before it can kill you.
The horizontal fraction bar was introduced by the Arabs.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The people with the highest levels of LDL are Mexican American males and non-Hispanic black females.