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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.
The first war in which wide-scale use of anesthetics occurred was the Civil War, and 80% of all wounds were in the extremities.
According to the CDC, approximately 31.7% of the U.S. population has high low-density lipoprotein (LDL) or "bad cholesterol" levels.
The most dangerous mercury compound, dimethyl mercury, is so toxic that even a few microliters spilled on the skin can cause death. Mercury has been shown to accumulate in higher amounts in the following types of fish than other types: swordfish, shark, mackerel, tilefish, crab, and tuna.
Sildenafil (Viagra®) has two actions that may be of consequence in patients with heart disease. It can lower the blood pressure, and it can interact with nitrates. It should never be used in patients who are taking nitrates.
![Changes in boreal forest composition along a chronosequence in Quebec. Dates refer to the year of th](https://biology-forums.com/gallery/47/medium_33_17_02_12_6_53_46_20121657.jpeg)
![Changes in boreal forest composition along a chronosequence in Quebec. Dates refer to the year of th](https://biology-forums.com/gallery/47/medium_33_17_02_12_6_53_46_20131094.jpeg)
![Changes in boreal forest composition along a chronosequence in Quebec. Dates refer to the year of th](https://biology-forums.com/gallery/47/medium_33_17_02_12_6_53_46_20141497.jpeg)