November 24, 2015
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Astigmatism Overview (cont.)

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What causes astigmatism?

Most astigmatism does not have a recognized cause, but merely is an anatomical imperfection in the shape of the cornea, where the front curvature of the cornea is toric, rather than spherical. A small amount of astigmatism is considered normal and does not represent a disease of the eye. This type of astigmatism is extremely common and frequently is present at birth or has its onset during childhood or young adulthood. There is some hereditary basis to most cases of astigmatism, and most people with astigmatism have it in both eyes in a symmetrical fashion. Astigmatism is often associated with myopia (nearsightedness) or hyperopia (farsightedness). Astigmatism can increase in amount during the growing years.

In regular astigmatism, the meridians in which the two different curves lie are located 90 degrees apart. Most astigmatism is regular. In irregular astigmatism, the two meridians may be located at something other than 90 degrees apart or there are more than two meridians.

A scar in the cornea, resulting from an injury or infection, may also cause astigmatism. Astigmatism can be caused by ocular surgery, including cataract surgery and corneal transplantation. Certain diseases of the eye, such as keratoconus or pellucid degeneration, will cause irregular astigmatism.

Who is at risk for astigmatism?

Individuals with a family history of high degrees of astigmatism or keratoconus are at risk for astigmatism. People who use power tools without safety glasses are subject to the type of injuries that may cause acquired astigmatism.

What are symptoms of astigmatism?

In an eye with astigmatism, vision is blurred due to the inability of the optical elements of the eye to focus a point object into a sharply focused point image on the retina. Astigmatism makes it difficult to see fine details, both close-up and at a distance. Small amounts of astigmatism may not be noticed at all. Sometimes uncorrected astigmatism can lead to eyestrain, eye fatigue, squinting, or headaches in addition to blurring and distortion of vision at all distances.

Medically Reviewed by a Doctor on 11/20/2015


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