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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

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
  • Peripheral corneal-relaxing incisions—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:

Astigmatism. American Academy of Ophthalmology website. Available at: https://www.aao.org/eye-health/diseases/what-is-astigmatism. Updated March 1, 2017. Accessed December 14, 2017.
Astigmatism. American Optometric Association website. Available at: https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/astigmatism. Accessed December 14, 2017.
Mozayan, E, Lee, J. Update on astigmatism management. Curr Opin Ophthalmol 2014 Jul;25(4):286-90.
Facts About Astigmatism. National Eye Institute website. Available at: https://nei.nih.gov/health/errors/astigmatism. Updated October 2010. Accessed December 14, 2017.
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.
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.
Last reviewed December 2017 by EBSCO Medical Review Board Michael Woods, MD
Last Updated: 12/20/2014

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