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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.
In 1864, the first barbiturate (barbituric acid) was synthesized.
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.
Patients who cannot swallow may receive nutrition via a parenteral route—usually, a catheter is inserted through the chest into a large vein going into the heart.
Fungal nail infections account for up to 30% of all skin infections. They affect 5% of the general population—mostly people over the age of 70.