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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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
It is widely believed that giving a daily oral dose of aspirin to heart attack patients improves their chances of survival because the aspirin blocks the formation of new blood clots.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Blood is approximately twice as thick as water because of the cells and other components found in it.