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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 two common types of astigmatism:

  • Corneal astigmatism—misshapen cornea
  • Lenticular astigmatism—misshapen lens
Normal Anatomy of the Eye
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Causes

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

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

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

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

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 three 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-assited 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 partial thickness 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

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

Revision Information

  • Eye Smart—American Ophthalmology

    http://www.geteyesmart.org

  • National Eye Institute (NEI)

    http://www.nei.nih.gov

  • Canadian Ophthalmological Society

    http://www.cos-sco.ca

  • The Canadian National Institute for the Blind

    http://www.cnib.ca

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