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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.
A good example of polar molecules can be understood when trying to make a cake. If water and oil are required, they will not mix together. If you put them into a measuring cup, the oil will rise to the top while the water remains on the bottom.
More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.
After 5 years of being diagnosed with rheumatoid arthritis, one every three patients will no longer be able to work.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.