Astigmatism is distorted vision caused by an unevenly curved cornea. The cornea is the clear outer layer on the front of the eye. As a result of astigmatism, your vision is somewhat blurry all the time.
Astigmatism is a common problem. Many people have astigmatism that is so slight that it does not interfere with their vision. People with worse astigmatism may squint to try to bring objects into focus. Squinting does not hurt your eyes, but it may lead to headaches.
No one knows for sure what causes uneven corneas. Corneas, like sets of teeth, are rarely perfect. Astigmatism sometimes runs in families. Some people have had irregular corneas since birth. Other people develop astigmatism as they get older. Astigmatism may develop after cataract or cornea surgery. People can have astigmatism along with nearsightedness (myopia) or farsightedness (hyperopia).
The main symptom is vision that is never completely clear and sharp at any distance or in any amount of light, without glasses. Part of your vision may be in focus and part blurry. For example, vertical lines may be in focus while horizontal lines are blurry.
Your eye care provider will test your vision and examine your eyes. You will be asked to read letters from a chart. Then you will be asked to read the same chart with different lenses in front of your eyes to see which ones improve your vision. Your provider may use a special instrument to focus a circle of light on the cornea and measure its reflection. This helps measure the curve of the cornea's surface.
Your provider will also check if you have any eye diseases.
For slight astigmatism, you may not need glasses. Greater degrees of astigmatism can be corrected with glasses or contact lenses.
Surgeons can treat astigmatism in some people by reshaping the cornea. Three procedures used are:
The main risks of these procedures are:
Be sure you talk to a qualified ophthalmologist (a medical eye doctor) about all your options before you decide which treatment is best for you.
Because there is no known cause for astigmatism, there is nothing you can do to prevent it.