Astigmatism is a very common condition or refractive error^1^ which relates to the shape of the eye. There are different types of astigmatism; corneal astigmatism is where the front surface of the eye has irregular curvature^1^. In some astigmatic eyes, the cornea can be even in shape. This would be known as lenticular astigmatism^1^. Corneal astigmatism is more common and is often described as a rugby ball shaped eye. Depending on the strength of astigmatism, it will generally result in vision being blurry or distorted^2^.
The most common type of astigmatism is termed as regular astigmatism. This is when light will cause the curves of the cornea to produce two different points of focus that if uncorrected, will not form a sharp image onto the retina. It is not unusual for people with myopia (short-sightedness) or hyperopia (long-sightedness) to have astigmatism as well. With regular astigmatism, these curves lay 90º apart or put another way, are perpendicular to each other^2^.
A more unusual type of astigmatism is termed as irregular, where the curves are not perpendicular to each other. This can be caused by injury to the cornea, scarring, surgery or by conditions such as keratoconus^2^.
Astigmatism is a common refractive error of the eye. In a study of over 11,000 spectacle wearers in the UK (both children and adults), 47.4% had astigmatism of 0.75 dioptres or greater in at least one eye, and 24.1% had this amount of astigmatism in both eyes^3^.
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