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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.
Side effects from substance abuse include nausea, dehydration, reduced productivitiy, and dependence. Though these effects usually worsen over time, the constant need for the substance often overcomes rational thinking.
According to the National Institute of Environmental Health Sciences, lung disease is the third leading killer in the United States, responsible for one in seven deaths. It is the leading cause of death among infants under the age of one year.
The human body produces and destroys 15 million blood cells every second.
Vampire bats have a natural anticoagulant in their saliva that permits continuous bleeding after they painlessly open a wound with their incisors. This capillary blood does not cause any significant blood loss to their victims.