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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.
Multiple sclerosis is a condition wherein the body's nervous system is weakened by an autoimmune reaction that attacks the myelin sheaths of neurons.
About 100 new prescription or over-the-counter drugs come into the U.S. market every year.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.