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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.
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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
Despite claims by manufacturers, the supplement known as Ginkgo biloba was shown in a study of more than 3,000 participants to be ineffective in reducing development of dementia and Alzheimer’s disease in older people.