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Astigmatism is an eye disorder in which the cornea (the clear tissue covering the front of the eye) is abnormally curved, causing out-of-focus vision.

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.

An astigmatism makes it difficult to see fine details, either close-up or from a distance.

Astigmatism is easily diagnosed by a standard ophthalmic exam with refraction test. Special tests are not usually required. 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).

Glasses or hard contact lenses will correct astigmatism. Soft contact lenses do not work as well.

Severe astigmatism can be treated with surgery.

Vision is usually normal with the correct glasses or contact lenses.

Astigmatism in only one eye may cause amblyopia.

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

Updated by: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.