How to Correct Astigmatism

Astigmatism is a common visual problem that can be treated easily.

It occurs when a shaped cornea or lens stops the eye from focusing light properly. In this article we will explain how to correct astigmatism by ensuring that light entering the eye is properly focused.

Often astigmatism is hereditary. However, it also occurs when eye surgery has left scars on the cornea or if you have sustained an injury to your eye. Conditions such as keratoconus that affect the shape of the cornea will also result in astigmatism

Normal vision and astigmatism

In normal vision, the cornea and the lens work together to refract the light that enters the eye through the pupil. The eye is shaped so that the refraction, or bending of the light, happens in exactly the right way to focus the light perfectly and produce an accurate image on the retina.

A patient with astigmatism experiences a refractive error, caused by the shape of the cornea or the lens. Typically, their eyes will be shaped more like an oval than a perfect sphere. This means that their vision will be blurred or distorted because the light rays are not coming together and focusing in the right place as two points of focus exist.

Astigmatic corneas can be rugby-ball shaped – this is called regular astigmatism and is the most common kind. Alternatively you may have a cornea which curves in different directions and has some areas thicker than others – this is called irregular astigmatism and is much rarer. Usually, astigmatism is present from birth, and is identified during routine eye tests.

If you have astigmatism you may have trouble reading, particularly if the print is small. You may also squint and suffer from headaches and fatigue. While some cases of astigmatism are very mild and need no treatment, others are more severe and will require treatment to correct the patient’s vision.

If you do not have astigmatism, the lines will appear sharply focused and equally dark in the diagram on the right.

Correcting the focus in a patient with astigmatism

If you are wondering how to correct an astigmatism, the treatment options are outlined below. To restore a patient’s vision, a change needs to be made so that the light can be focused properly once more. This can be done either by using external corrective lenses (glasses or contact lenses) or through surgery (laser eye surgery or lens implants with toric – astigmatism correcting intraocular lenses).

Corrective lenses

There are three main types of corrective lenses for astigmatism.

• Wearing glasses with cylindrical lenses will adjust the way that the eye can focus light, correcting the patient’s vision. It’s a simple and effective way to correct astigmatism.

• Soft contact lenses do the same job as glasses in changing the way the light is focused.

• Rigid gas permeable lenses (RGP for short) hold their shape firmly, meaning that light coming into the eye hits a spherical surface, rather than the abnormal surface of the naked astigmatic eye. For this reason they are often more effective than soft contact lenses in correcting an astigmatism, but they can also be uncomfortable for some patients.

Laser eye surgery

Contrary to what you may have heard, astigmatism can be treated with laser eye surgery. This is a quick and non-invasive procedure that uses a laser to change the shape of the cornea, thereby altering the path of the light that enters the eye. The laser procedure will also correct your long- or short-sightedness if this is present.

Patients undergoing laser eye surgery report better vision as early as 24 hours following the procedure, which takes around 15 minutes total for both eyes. One eye can be corrected immediately after the other.

Clear lens extraction

This is a surgical procedure to insert a lens into the eye – known as an intraocular lens (IOL). The IOL will correct the astigmatism and help the patient regain superior vision.

More invasive than laser eye surgery, clear lens extraction can nevertheless be a good option for patients who are undergoing cataract surgery at the same time, or for those who are not eligible for laser eye surgery.