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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.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
A seasonal flu vaccine is the best way to reduce the chances you will get seasonal influenza and spread it to others.