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A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
The strongest synthetic topical retinoid drug available, tazarotene, is used to treat sun-damaged skin, acne, and psoriasis.
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).