Astigmatism
What is astigmatism?
Astigmatism is a condition where the front surface of the eye (the cornea) or the lens inside the eye is irregularly shaped and causes the vision to be distorted. For example, instead of having a round, spherical curvature like a basketball, the cornea may be elongated like a rugby ball. Light rays entering an astigmatic eye are bent unevenly. As a result, these rays do not focus at a single point on the retina, causing both near and far away objects to be blurred.
There are a number of different types of astigmatism. These include:
- compound;
- corneal;
- hypermetropic;
- hyperopic;
- irregular;
- lenticular;
- mixed;
- myopic; and
- regular.
Causes
Astigmatism is not a disease and often occurs with near-sightedness and far-sightedness. The exact cause remains unknown; however, some common types of astigmatism seem to run in families and may be inherited. It is thought that most people have some form of astigmatism as it is rare to find perfectly shaped curves in the cornea and lens, but the defect is rarely serious.
Symptoms
Blurred or distorted vision, eye strain and headaches are possible symptoms of astigmatism.
What your doctor can do for you
- Perform an eye examination to determine whether you have astigmatism.
- Refer you to an optometrist for correction of the astigmatism with prescription glasses or contact lenses.
- Refer you to an ophthalmologist (eye specialist) for laser eye surgery, which can help correct certain types of astigmatism, or for astigmatic keratotomy, another surgical procedure that is carried out less often nowadays.
Last Reviewed: 04 November 2009
- 1. American Optometric Association. Astigmatism [Website]. http://www.aoa.org/x4698.xml (accessed March 2010).
2. Mayo Foundation for Medical Education and Research. Astigmatism [Website]. Jan 2009. http://www.mayoclinic.com/print/astigmatism/DS00230/DSECTION=all&METHOD=print (accessed March 2010).
