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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.
Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.
Cyanide works by making the human body unable to use oxygen.