Astigmatism is distorted vision caused by an unevenly curved
cornea (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 more astigmatism may squint
to try to bring objects into focus. Squinting does not hurt
your eyes, but it may lead to headaches.
Astigmatism can occur with nearsightedness (myopia) or
farsightedness (hyperopia). Astigmatism can be treated with
eyeglasses, contact lenses, or surgery.
How does it occur?
No one knows for sure what causes uneven corneas. Corneas,
like sets of teeth, are rarely perfect. Astigmatism tends
to run in families. Some people have had irregular corneas
since birth. Other people develop astigmatism as they get
older when the cornea, like skin and other tissues, loses
its flexibility.
Astigmatism may develop after cataract or cornea surgery.
What are the symptoms?
The main symptom is vision that is never completely clear
and sharp at any distance or in any amount of light. Part
of your vision may be in focus and part blurry. For
example, vertical lines may be in focus while horizontal
lines are blurry.
How is it diagnosed?
Your eye doctor 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 doctor may examine your eyes with special instruments to
see if you have any eye diseases.
How is it treated?
For slight astigmatism, you may not need glasses. Greater
degrees of astigmatism can be corrected with glasses or
contact lenses.
In recent years, surgeons have been able to treat
astigmatism in some people by reshaping the cornea. Three
procedures used are:
- AK (astigmatic keratotomy), in which the surgeon cuts small
slits in the peripheral cornea. This procedure flattens
the cornea, which often helps light rays focus better on
the retina.
- PRK (photorefractive keratectomy), in which the surgeon
uses a laser to remove thin layers of the cornea. This
changes the shape of the cornea and may allow better
focusing.
- LASIK (laser in situ keratomileusis), in which the surgeon
uses a laser and a very precise tool to reshape the
cornea.
The main risks of these procedures are:
- becoming more nearsighted or farsighted
- glare
- a worsening of the astigmatism
- infection of the eye.
Not everyone with astigmatism will benefit from these
procedures. 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.
How can I take care of myself?
Have your eyes checked every 2 or 3 years (at least every
2 years if you are over 40). See your eye doctor if your
vision gets worse.
Always wear goggles or safety glasses at work or recreation
where your eyes could be injured.
Can I help prevent astigmatism?
Because there is no known cause for astigmatism, there is
nothing you can do to prevent it.


Disclaimer: This content is reviewed periodically and is subject to
change as new health information becomes available. The
information provided is intended to be informative and educational and is not a
replacement for professional medical evaluation, advice, diagnosis or
treatment by a healthcare professional.
HIA File eye4224.HTM Release 9.0/2006. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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