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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 immune system needs 9.5 hours of sleep in total darkness to recharge completely.
There are 60,000 miles of blood vessels in every adult human.
Medication errors are three times higher among children and infants than with adults.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.