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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.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
Complications of influenza include: bacterial pneumonia, ear and sinus infections, dehydration, and worsening of chronic conditions such as asthma, congestive heart failure, or diabetes.
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.