Astigmatism (eye) (patient information)

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What is astigmatism?

Astigmatism is an eye disorder in which the cornea, the clear tissue covering the front of the eye, or sometimes the lens , is abnormally curved. An abnormally shaped cornea or lens does not allow light to properly focus on the retina, which causes out-of-focus vision.

What are the symptoms of astigmatism?

Although mild astigmatism may be asymptomatic, higher amounts of astigmatism may cause symptoms such as:

• Blurry vision
• Squinting
• Asthenopia
• Fatigue
• Headaches

What are the causes of astigmatism?

The cause of astigmatism is unknown. It is usually present from birth, and often occurs together with nearsightedness or farsightedness. A minor degree of astigmatism is considered normal and does not require correction. Astigmatism is very common.

Astigmatism may sometimes develop due after eye surgery or following an eye injury .

Additionally, severe astigmatism may result from a somewhat rare condition called keratoconus, which is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve.

Who is at risk for astigmatism?

According to an American study published in Archives of Ophthalmology, nearly 3 in 10 children between the ages of 5 and 17 have astigmatism . Regarding the prevalence in adults, a recent study in Bangladesh found that nearly 1 in 3 (32.4%) of those over the age of 30 had astigmatism.

How to know you have astigmatism?

Astigmatism is easily diagnosed by a typical comprehensive eye examination. Special tests are not usually required. Tests that may be performed during the eye exam may include :

• Visual acuity: The acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain.
• Keratometry: A keratometer is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism.
• Refraction: Lenses are placed in front of your eyes to determine which prescription provides the patient with the clearest vision.
• Retinoscopy: Children or others who cannot respond to questions can have the degree of their vision problem measured by a test that uses reflected light (retinoscopy).

When to seek urgent medical care

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

Treatment options

Many people have some degree of astigmatism, but those with a small amount of astigmatism do not experience vision problems and do not require treatment.

Glasses, hard contact lenses, and orthokeratology will correct astigmatism. Soft contact lenses do not work as well.

Severe astigmatism can be treated with surgery.

Where to find medical care for astigmatism

Directions to Hospitals Treating astigmatism

What to expect (Outlook/Prognosis)

The outlook of those with an astigmatism is generally very good, provided that treatment is available. Vision is usually normal with the correct glasses or contact lenses.

Sources

http://www.nlm.nih.gov/medlineplus/ency/article/001015.htm