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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.
Hyperthyroidism leads to an increased rate of metabolism and affects about 1% of women but only 0.1% of men. For most people, this increased metabolic rate causes the thyroid gland to become enlarged (known as a goiter).
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.