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Did you know?
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.
Did you know?
There are more sensory neurons in the tongue than in any other part of the body.
Did you know?
The horizontal fraction bar was introduced by the Arabs.
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Vaccines prevent between 2.5 and 4 million deaths every year.
Did you know?
Approximately 15–25% of recognized pregnancies end in miscarriage. However, many miscarriages often occur before a woman even knows she is pregnant.