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Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Individuals are never “cured” of addictions. Instead, they learn how to manage their disease to lead healthy, balanced lives.
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.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.