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Astigmatism

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What is astigmatism?

Astigmatism is an optical defect that interferes with the eye's ability to focus sharply, so it can result in unclear vision. It occurs because the shape of the cornea (the clear focusing surface that overlies the colored iris) is not perfectly round like a marble, but more oval like a spoon. Almost everyone is born with some astigmatism, though the amount may be so small that it isn't important. Heredity is the most common cause of astigmatism. It does not come from reading or using your eyes "too much" or reading in dim light.

What's it Like to Have Astigmatism?

Astigmatic images are never sharp and crisp, either close up or in the distance. If you have a large amount of astigmatism, your vision may be very blurred. Straight lines running in one direction may be more blurred than lines running in another; for example, only the vertical edges of a window may appear out-of-focus. As you try to overcome the blur and see more clearly, you might get a headache from continually contracting the muscles around your eyes and furrowing your brows (actions that may be so automatic that you aren't aware of them).

How Is Astigmatism Corrected?

Astigmatism can be optically corrected, and vision sharpened, by prescription eyeglasses. (A small amount may require no correction if it does not affect your vision or cause eyestrain or headaches.) Glasses can also reduce the ocular pulling, dizziness, or difficulty with sustained reading. At first, the glasses can make objects look a bit tilted or distorted, but this should disappear after you get used to them. Rigid, gas permeable contact lenses can also be used to correct astigmatism. Soft lenses cannot be used, unless they are special "toric" lenses that are made to compensate for the astigmatic shape of the corneas. The amount of time you wear your correction will not have any effect on the basic astigmatism or its development-- that is, wearing glasses or contacts will neither make the astigmatism better or worse.

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