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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.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
Vital signs (blood pressure, temperature, pulse rate, respiration rate) should be taken before any drug administration. Patients should be informed not to use tobacco or caffeine at least 30 minutes before their appointment.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.