Causes and Risk Factors of Irregular Astigmatism

Causes and Risk Factors of Irregular Astigmatism

irregular credit astigmatism can be frustrating as you cannot see well at any distance without correction.

With regular astigmatism, light entering the eye lands on two different points instead of being refracted into one. This is due to the irregular shape of the eye or lens (the transparent part inside the eye that directs the rays to the light-sensitive retina at the back of the eye).

The problem is usually that instead of the eye being round and even, like a volleyball, it is somewhat elongated, like a soccer ball, with more curve in one area than another.

But with irregular astigmatism, the surface of the eye can be uneven in different ways instead of just one. This can cause several different focal points, resulting in blurred vision.

This article will examine the common causes of irregular astigmatism and the role of genetic and lifestyle factors in this condition.

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Common causes

Irregular astigmatism can be caused by the following:

  • Surface trauma, such as an injury with a stick or branch
  • Degenerative eye diseases such as keratoconusin which the cornea (the clear dome at the front of the eye) may develop a cone-like surface, or anterior basement membrane dystrophy, in which the cornea loses strength and becomes uneven
  • Corneal surgery, such as laser-assisted keratomileusis in situ (LASIK) with a complication such as an off-center removal of the cornea (the clear surface that is reshaped by the excimer laser) or a flap problem


Some conditions known to cause irregular astigmatism, such as the following, have a genetic component. Such conditions can leave the cornea vulnerable to irregular astigmatism.


With keratoconus, the cornea thins and bulges forward, stiffening into a cone shape. It causes refractive problems such as myopia (in which distance vision is blurry) and also irregular astigmatism. This is the result of environmental factors such as eye rubbing, as well as genetics.

Up to 23% of people with keratoconus have a family history of it. It seems that genes can predispose some to keratoconus, usually when it is combined with environmental or other factors. Some genes that appear to play a role in keratoconus include:

  • VSX1 gene: This gene is also associated with corneal dystrophy, which involves changes in one or more of the layers of the cornea.
  • SOD1 gene: This gene is associated with reactive oxygen species (generated by cell metabolism) that can cause cell death.
  • ZNF469 gene: This gene is linked to fragile cornea syndrome, a disease involving thinning of the cornea.
  • TGFI gene: This gene is associated with cell-collagen interactions.

Anterior basement membrane dystrophy

With anterior basement membrane dystrophy, the outer layer of the cornea does not grow properly and may erode. The epithelial basement membrane itself becomes thickened and very irregular, making your vision blurry. It may be an inherited disorder associated with the transforming growth factor beta (TGFBI)-mediated gene.

Lifestyle risk factors

While the risk factors for irregular astigmatism may be beyond your control in some cases, in others the way you live your life can have an impact. You can, for example, avoid undergoing a refractive procedure such as LASIK, in which the development of irregular astigmatism can be a complication.

Also, if you engage in activities (especially outdoors) that can cause eye injury, be sure to wear eye protection. Environmental factors can affect those predisposed to keratoconus and those who are not.

Here are some potential factors to try to avoid:

  • Eye rubbing: About half of people with keratoconus rub their eyes. This can last up to 180 seconds, as opposed to the typical five seconds of friction in people without this condition. Some believe that a little trauma to the epithelium from friction can contribute to increased inflammation and other activity in the area.
  • Sun exposure: Those who live in warm, sunny places are more likely to develop keratoconus than those who live in more shady areas. This may be the result of reactive oxygen species being caused by exposure to ultraviolet light.
  • Nicotine use: Smoking cigarettes can increase the risk of developing keratoconus in some cases.


Having irregular astigmatism can leave you with blurry vision at all distances. Blurring occurs because the cornea (which focuses light on the back of the eye) cannot focus on a single point. With irregular astigmatism, where the corneal surface is uneven, there may be several different focal points.

Irregular astigmatism can be caused by accidental trauma, degenerative eye disease, or a complication of eye surgery such as LASIK. Genetics can play a role in the development of conditions such as keratoconus and anterior basement membrane dystrophy which can lead to the development of irregular astigmatism.

Additionally, lifestyle factors such as eye rubbing, sun exposure, and smoking may play a role in the development of certain irregular astigmatism-related conditions.

A word from Verywell

Although it is preferable and possible to avoid irregular astigmatism in some cases, it will not be possible in others. Nevertheless, being alert to potential causes can help you minimize the difficulties associated with this condition.

Verywell Health only uses high quality sources, including peer-reviewed studies, to support the facts in our articles. Read our editorial process to learn more about how we fact check and ensure our content is accurate, reliable and trustworthy.

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  2. Journal of ophthalmology. A rational approach to irregular astigmatism.

  3. Loukovitis E, Sfakianakis K, Syrmakesi P, et al. Genetic aspects of keratoconus: a review of the literature exploring potential genetic contributions and possible genetic relationships with comorbidities. Ophthalmol Ther. 2018;7(2):263-292. doi:10.1007/s40123-018-0144-8

  4. National Institute of Health. Epithelial dystrophy of the basement membrane.

  5. Gordon-Shaag A, Millodot M, Shneor E, Liu Y. Genetic and environmental factors of keratoconus. BioMed Research International. 2015;2015:1-19. doi:10.1155/2015/795738

By Maxine Lipner

Maxine Lipner is a longtime medical and health writer with over 30 years of experience in the fields of ophthalmology, oncology, and general health and wellness.

#Risk #Factors #Irregular #Astigmatism

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