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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.
Lower drug doses for elderly patients should be used first, with titrations of the dose as tolerated to prevent unwanted drug-related pharmacodynamic effects.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.