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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?
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
Did you know?
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Did you know?
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
Did you know?
Your heart beats over 36 million times a year.