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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 60,000 miles of blood vessels in every adult human.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Oliver Wendell Holmes is credited with introducing the words "anesthesia" and "anesthetic" into the English language in 1846.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.