Astigmatism (eye) (patient information)

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 * Assistant Editor(s)-In-Chief: Erin E. Lord

Overview
Astigmatism is a common eye disorder that is a type of refractive error. It is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye, due to an abnormally shaped cornea. An astigmatism often causes out-of focus vision.

What are the symptoms of Astigmatism?
Astigmatism may cause symptoms such as  :
 * Blurry vision
 * Squinting
 * Asthenopia
 * Fatigue
 * Headaches
 * Difficulty driving at night

It is possible to have mild astigmatism and not know about it. This is especially true for children, who are not aware of their vision being other than normal. Some adults may also have mild astigmatism without any symptoms. It's important to have comprehensive dilated eye exams to make sure you are seeing at your best.

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 highest risk?
Astigmatism can affect both children and adults. 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. A number of studies have found that the prevalence of astigmatism increases with age.

Some patients with slight astigmatism will not notice much change in their vision. It is important to have eye examinations at regular intervals in order to detect any astigmatism early on for children.

Diagnosis
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
Astigmatism can be corrected with eyeglasses, contact lenses, or surgery. Individual lifestyles affect the way astigmatism is treated.

Eyeglasses are the simplest and safest way to correct astigmatism. Your eye care professional will prescribe appropriate lenses to help you see as clearly as possible.

Contact Lenses work by becoming the first refractive surface for light rays entering the eye, causing a more precise refraction or focus. In many cases, contact lenses provide clearer vision, a wider field of vision, and greater comfort. They are a safe and effective option if fitted and used properly. It is very important to wash your hands and clean your lenses as instructed in order to reduce the risk of infection.

If you have certain eye conditions you may not be able to wear contact lenses. Discuss this with your eye care professional.

Refractive surgery aims to change the shape of the cornea permanently. This change in eye shape restores the focusing power of the eye by allowing the light rays to focus precisely on the retina for improved vision. There are many types of refractive surgeries. Your eye care professional can help you decide if surgery is a good option for you.

Where to find medical care for Astigmatism?
Directions to Hospitals Treating astigmatism

Prevention of Astigmatism
Astigmatism cannot be prevented, but it can be prevented from getting worse by following an appropriate treatment regimen. Therefore, it is very important to have regular comprehensive eye examinations.

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.

Additional links
http://www.nlm.nih.gov/medlineplus/ency/article/001015.htm http://www.nei.nih.gov/healthyeyes/astigmatism.asp