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Astigmatism

Definition

Astigmatism is a type of refractive error of the eye. Refractive errors cause blurred vision and are the most common reason why a person goes to see an eye professional.

Other types of refractive errors are:

Causes, incidence, and risk factors

People are able to see because the front part of the eye (cornea) is able to bend (refract) light and focus it onto the back surface of the eye, called the retina.

 If the light rays are not clearly focused on the retina, the images you see may be blurry.

With astigmatism, the cornea is abnormally curved, causing vision to be out of focus.

The cause of astigmatism is unknown. It is usually present from birth, and often occurs together with nearsightedness or farsightedness.

Astigmatism is very common. It sometimes occurs after certain types of eye surgery, such as cataract surgery.

Symptoms

Astigmatism makes it difficult to see fine details, either close up or from a distance.

Signs and tests

Astigmatism is easily diagnosed by a standard eye exam with refraction test. Special tests are not usually required.

Children or others who cannot respond to a normal refraction test can have their refraction measured by a test that uses reflected light (retinoscopy).

Treatment

Mild astigmatism may not need to be corrected.

Glasses or contact lenses will correct astigmatism, but do not cure it.

Laser surgery can help change the shape of the cornea surface to eliminate astigmatism, along with nearsightedness or farsightedness.

Expectations (prognosis)

Astigmatism may change with time, requiring new glasses or contact lenses. Laser vision correction can usually eliminate, or greatly reduce, astigmatism.

Complications

In children, uncorrected astigmatism in only one eye may cause amblyopia.

Calling your health care provider

Call for an appointment with your health care provider or ophthalmologist if vision problems worsen, or do not improve with glasses or contact lenses.

References

Olitsky SE, Hug D, Plummer L, Stass-Isern M. Abnormalities of refraction and accommodation. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 612.

White PF, Scott CA. Contact lenses. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, Mo: Mosby Elsevier; 2008:chap 2.9.

Kramarevsky N, Hardten DR. Excimer laser photorefractive keratectomy. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, Mo: Mosby Elsevier; 2008:chap 3.4.


Review Date: 9/3/2012
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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