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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.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
Persons who overdose with cardiac glycosides have a better chance of overall survival if they can survive the first 24 hours after the overdose.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
About 100 new prescription or over-the-counter drugs come into the U.S. market every year.