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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.
Patients who have undergone chemotherapy for the treatment of cancer often complain of a lack of mental focus; memory loss; and a general diminution in abilities such as multitasking, attention span, and general mental agility.
The longest a person has survived after a heart transplant is 24 years.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.