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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.
More than 34,000 trademarked medication names and more than 10,000 generic medication names are in use in the United States.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).