|
|
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.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
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.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.