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Astigmatism

Definition

Astigmatism is a condition that results in blurred, unfocused, or fuzzy vision. The cornea (the front surface of the eye) or lens (located behind the cornea) has an abnormal or irregular curve.

There are 2 common types of astigmatism:

  • Corneal astigmatism—misshapen cornea
  • Lenticular astigmatism—misshapen lens

Normal Anatomy of the Eye

Copyright © Nucleus Medical Media, Inc.

Causes    TOP

The precise cause of astigmatism is unknown. It is often present at birth and may coexist with nearsightedness or farsightedness. Sometimes, it may occur after an injury or eye surgery.

Risk Factors    TOP

Factors that may increase your chance of astigmatism include:

  • Heredity—a family history of astigmatism, eye disease, or disorders such as keratoconus
  • Eye surgery—certain types of eye surgery, such as cataract removal
  • A history of corneal scarring or thinning
  • A history of excessive nearsightedness or farsightedness

Symptoms    TOP

Some people with astigmatism may have no symptoms. In those that have symptoms, astigmatism may cause:

  • Blurred or distorted vision, which may cause you to squint
  • Headaches
  • Lightheadedness

Symptoms vary depending on the extent of the astigmatism.

Diagnosis    TOP

Your eye doctor will ask about your symptoms and medical history. An examination of your eyes will be done.

Tests to evaluate your eyes may include:

  • Visual acuity assessment test (VAT)—to assess distant vision
  • Refractor test
  • Keratoscope—to detect and measure the presence of corneal surface curvature

Treatment    TOP

Treatment options may include the following:

Corrective Lenses

Corrective lenses, such as glasses or toric contact lens, are prescribed to offset the eye’s visual abnormalities or defects.

Surgery

To correct severe astigmatism, your eye surgeon might use special knives or a laser beam to correct the abnormal or irregular curve of the cornea.

There are 3 types of surgical procedures that an eye surgeon might perform:

  • Photorefractive keratectomy (PRK)—laser beams are used to reshape the abnormal or irregular curve of the cornea
  • Laser-assisted in situ keratomileusis (LASIK)—laser beams used to reshape the curve of the cornea by removing corneal tissue
  • Radical keratotomy (RK)—small incisions (cuts) are made into the cornea
  • Laser-assisted subepithelial keratomileusis (LASEK)—not as commonly used, but it may benefit people with thin corneas, or those at high risk of an eye injury

Prevention    TOP

There are no current guidelines to prevent astigmatism. See your eye doctor for regular check-ups.

RESOURCES:

Eye Smart—American Ophthalmology
http://www.geteyesmart.org
National Eye Institute (NEI)
http://www.nei.nih.gov

CANADIAN RESOURCES:

Canadian Ophthalmological Society
http://www.cos-sco.ca
The Canadian National Institute for the Blind
http://www.cnib.ca

References:

Condon PI, Mulhern M, et al. Laser intrastromal keratomileusis for high myopia and myopic astigmatism. Br J Ophthalmol. 1997;81(3):199-206.
Goss DA. Refractive error changes in mixed astigmatism. Ophthalmic Physiol Opt. 1999;19(5):438-40.
Holladay JT, Moran JR, et al. Analysis of aggregate surgically induced refractive change, prediction error, and intraocular astigmatism. J Cataract Refract Surg. 2001;27(1):61-79.
Komaroff AL, ed. Harvard Medical School Family Health Guide. New York, NY: Simon and Schuster; 1999:423-425.
Kymionis GD, Aslanides M, et al. Laser in situ keratomileusis for residual hyperopic astigmatism after conductive keratoplasty. J Refract Surg. 2004;20(3):276-278.
Miller JM, Dobson V, et al. Comparison of preschool vision screening methods in a population with a high prevalence of astigmatism. Invest Ophthalmol Vis Sci. 2001;42(5):917-924.
Pesudovs K. Autorefraction as an outcome measure of laser in situ keratomileusis. J Cataract Refract Surg. 2004;30(9):1921-1928.
Taneri S, Feit R, et al. Safety, efficacy, and stability indices of LASEK correction in moderate myopia and astigmatism. J Cataract Refract Surg. 2004;30(10):2130-2137.
Tobaigy FM, Ghanem RC, et al. A Control-matched comparison of laser epithelial keratomileusis and laser in situ keratomileusis for low to moderate myopia. Am J Ophthalmol. 2006;142(6):901-908.
Varley GA, Huang D, et al. LASIK for hyperopia, hyperopic astigmatism, and mixed astigmatism: a report by the American Academy of Ophthalmology. Ophthalmology. 2004;111(8):1604-1617.
Last reviewed December 2014 by Michael Woods, MD
Last Updated: 12/20/2014

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