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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.
Drug-induced pharmacodynamic effects manifested in older adults include drug-induced renal toxicity, which can be a major factor when these adults are experiencing other kidney problems.
During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).
Vital signs (blood pressure, temperature, pulse rate, respiration rate) should be taken before any drug administration. Patients should be informed not to use tobacco or caffeine at least 30 minutes before their appointment.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).