Astigmatism is a condition where the cornea has an abnormal curvature, causing a distortion in vision. A normal cornea is shaped like a sphere but in astigmatism the cornea is oval-shaped, causing problems in focusing the light entering the eye. Astigmatism is a very common condition and often occurs together with myopia (short-sightedness) or hyperopia (long-sightedness).
The cause of astigmatism is often unknown. Astigmatism is usually present from birth. A small degree of astigmatism is considered normal and usually does not require any correction. Though rare, astigmatism may be caused by chronic vigorous eye rubbing (such as in children with allergic conjunctivitis) or by cornea diseases such as keratoconus.
Astigmatism can be corrected with corrective lenses such as in spectacles or contact lenses. They help to focus light entering the eye onto the retina. Other ways to correct astigmatism include refractive surgery options such as LASIK and implantable contact lenses.