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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.
Computer programs are available that crosscheck a new drug's possible trade name with all other trade names currently available. These programs detect dangerous similarities between names and alert the manufacturer of the drug.
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.
Cyanide works by making the human body unable to use oxygen.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.