Astigmatism Q&As
Published by Bupa's health information team, November 2008.
Answers to questions about astigmatism
This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.
- Is it possible to be long- or short-sighted as well as having astigmatism?
- Will I be able to wear contact lenses if I have astigmatism?
- What types of laser eye surgery can be used to correct astigmatism?
Is it possible to be long- or short-sighted as well as having astigmatism?
Yes. Often people with vision conditions such as short-sightedness (myopia) and long-sightedness (hyperopia) also have astigmatism.
Explanation
Astigmatism is often accompanied by vision conditions such as short-sightedness or long-sightedness. This may be due to the astigmatism as the curve of the cornea is not its usual round shape - it's oval.
With normal vision, when you look at something, light rays from an object pass into the eye through the cornea - the clear dome that covers the pupil - then through the lens towards the retina at the back of your eye. In a healthy eye, the lens and cornea focus the light rays on a small area of the retina so that you can see the object clearly.
With short-sightedness, the cornea can be too curved, whereas with long-sightedness the cornea may not be curved enough. This causes light rays entering the eye to focus in front of the retina (short-sightedness) or behind the retina (long-sightedness). With astigmatism, the cornea is curved unevenly, causing the light rays to focus either behind the retina (hyperopic astigmatism) or in front of the retina (myopic astigmatism).
However, astigmatism is not always the cause of long-sightedness or short-sightedness.
If you have long-sightedness or short-sightedness and have astigmatism, your optometrist will prescribe lenses to correct for both vision conditions.
Further information
The College of Optometrists
020 7839 6000
www.college-optometrists.org
Sources
Astigmatism. American Optometric Association. www.aoa.org, accessed 1 January 2008
Will I be able to wear contact lenses if I have astigmatism?
Yes, you can wear contact lenses if you have astigmatism
Explanation
A common misconception is that astigmatism can only be corrected by glasses, not by contact lenses. However, this is not the case. Astigmatism can be corrected using hard or gas-permeable contact lenses and, more recently, by soft contact lenses (toric lenses).
Hard contact lenses are very good at correcting astigmatism because they are rigid. This helps the cornea to hold a more evenly curved shape. Often people find hard lenses difficult to get used to. Also, they can only be worn during the day. Nowadays, hard lenses are becoming less commonly used.
Gas-permeable contact lenses can be used to treat astigmatism, although they are less effective than hard lenses. This is because they are only semi-rigid. Most people find them more comfortable than hard lenses, as they allow oxygen to flow through to the cornea, whereas hard lenses don't.
In recent years, toric lenses have become available to correct astigmatism. These are soft contact lenses. Usually, soft contact lenses can't be used to treat astigmatism because they wrap to the shape of the cornea, unlike hard lenses that rigidly fit to and re-shape the cornea. However, toric lenses can be made so that one part of the lens corrects for a more uneven corneal surface than the other. In general, people find soft contact lenses more comfortable to wear.
Talk to your optometrist to discuss which option is best for you.
Further information
The College of Optometrists
020 7839 6000
www.college-optometrists.org
Sources
Khaw PT and Elkington AR. ABC of Eyes. London: BMJ Publishing Group, 2002
What types of laser eye surgery can be used to correct astigmatism?
Several types of laser eye surgery can be used to treat astigmatism; these include LASIK, LASEK and PRK.
Explanation
Laser eye surgery is a surgical technique used to treat refractive errors, reducing the need for glasses or contact lenses. A refractive error is an error in the amount your eye bends light rays - this includes short-sightedness (myopia), long-sightedness (hyperopia) and astigmatism. Often astigmatism is accompanied by short-sightedness or long-sightedness - laser eye surgery will correct for both conditions (if you have both).
The following laser surgery techniques are used:
- LASIK (laser-assisted in situ keratomileusis)
- LASEK (laser epithelial keratomileusis)
- PRK (excimer laser photorefractive keratectomy)
All of the above techniques use an excimer laser (a computer-controlled laser) to even out the curve of the cornea, changing it from an oval shape to a round shape. This allows light rays entering your eye to correctly focus on the retina.
Surgery is usually done under local anaesthesia. This completely blocks feeling from your eye and you will stay awake during the operation.
In LASIK surgery, a highly precise instrument called a microkeratome is used to make an ultra-thin flap (no thicker than cling film) in your cornea. The flap is 'opened' (like the cover of a book) so that the laser can be used to shape the cornea underneath. The excimer laser is then used to remove precisely the right amount of corneal tissue to re-shape your cornea. The flap will then be repositioned and bonded to the rest of your cornea.
With LASEK, alcohol is used to loosen the surface layer of the cornea (epithelium), which is lifted as a flap. The excimer laser is then used to re-shape the cornea. Once this has been completed, the flap of epithelium is replaced.
PRK is the oldest technique. The epithelium is cut out before the excimer laser is used directly on the cornea. Less of the cornea is removed than in the other two procedures.
There are many benefits to having laser eye surgery; however, there are also possible side-effects and complications. Before deciding on treatment it's important to discuss these thoroughly with your ophthalmologist (a doctor specialising in eye health).
Further information
The College of Optometrists
020 7839 6000
www.college-optometrists.org
Sources
- Patient's guide to excimer laser refractive surgery. The Royal College of Ophthalmologists. www.rcophth.ac.uk, accessed 12 February 2008
- National Institute for Health and Clinical Excellence (NICE). Photorefractive (laser) surgery for the correction of refractive errors. Interventional Procedure Guidance 164. March 2006 www.nice.org.uk
Related topics
This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr Tim Cripps DM, FRCP, Consultant Cardiologist, specialist in electrophysiology, Bristol Royal Infirmary, and by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: November 2008.
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