Astigmatism

Astigmatism is a condition where the front of the eye is not perfectly round. Some cases are mild and require no treatment, but others cause poor vision. It can be corrected with glasses, contact lenses and laser eye surgery.

Astigmatism explanation diagram

What is astigmatism?

If the transparent layer of tissue called the cornea at the front of your eye is not spherical and evenly curved, you have astigmatism. This will probably have been present from birth, and identified during a routine eye examination.

Your optician will tell you which type you have:

Regular: the most common and is the name given to the condition where your corneas are rugby-ball shaped i.e. more curved in one meridian compared to the other.

Irregular: is much rarer, and describes a cornea which curves in different directions and has some areas thicker than others.

What causes astigmatism?

What causes astigmatism?

Often, astigmatism is hereditary. However, it can also occur as a result of scarring, previous surgery or previous injury to the eye. Certain eye conditions can also affect the shape of the cornea and can result in this condition, like keratoconus and pterygia.

A laser eye surgery examining a patient for astigmatism

Why is it a problem?

Like long and short sightedness, astigmatism is a refractive error. The rugby-ball shape of the eye means that light enters at different angles than it would if the eye were perfectly round. The result is that you have two points of focus rather than one, so the image you see is blurred. For example you may have trouble reading, particularly if the print is small. You may also squint and suffer from headaches and fatigue.

How to correct it

Glasses, contact lenses and laser eye surgery are all appropriate methods of treatment.

For those seeking to correct this condition with laser eye surgery, the LASIK procedure is the most commonly performed, although the alternative LASEK procedure is also available if LASIK is contraindicated. It is slightly more complicated to treat compared to long- and short-sightedness, because the mathematical algorithms that guide the laser remodelling are slightly more complex. Most modern lasers can treat up to 6 dioptres of reliably.