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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.
The familiar sounds of your heart are made by the heart's valves as they open and close.
There are more bacteria in your mouth than there are people in the world.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
More than 30% of American adults, and about 12% of children utilize health care approaches that were developed outside of conventional medicine.