Irregular Astigmatism: Causes and Risk Factors

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irregular existence Astigmatism It can be frustrating because you can’t see well at any distance without correction.

With regular astigmatism, light entering the eye falls at two different points rather than being refracted to just one point. This is caused by the irregular shape of the eye or the lens (the clear part inside the eye that directs rays to the light-sensitive retina at the back of the eye).

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

But in the case of irregular astigmatism, the surface of the eye can be uneven in many different ways rather than just one way. This can cause several different points of focus, resulting in blurred vision.

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

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Common causes

Irregular astigmatism can be caused by:

  • A bruise on the surface, such as being hit with a stick or a sprig
  • Degenerative eye diseases such as keratoconusat any cornea (the transparent dome in the front of the eye) can develop conical on the surface, or anterior basement membrane dystrophy, in which the cornea loses its strength and becomes uneven
  • Corneal surgery, such as laser-assisted in situ keratoplasty (LASIK) with complications such as eccentric keratectomy (the clear surface that is reshaped by the excimer laser) or a flap problem

Genetics

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

keratoconus

With keratoconus, the cornea thins and bulges forward, descending into a conical shape. It causes refractive problems such as nearsightedness (where far vision is blurry) as well as irregular astigmatism. This is the result of environmental factors such as eye rubbing, as well as genetic factors.

Up to 23% of people with keratoconus have a family history of keratoconus. It appears that genes may predispose some to keratoconus, usually when combined with one or another environmental factors. Some of the genes that seem to play a role in keratoconus include:

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

anterior basement membrane atrophy

With atrophy of the anterior basement membrane, the outer layer of the cornea does not develop properly and may erode. The epithelial basement membrane itself becomes thickened and very irregular, causing your vision to become blurred. This could be a genetic condition linked to the TGFBI gene.

Lifestyle Risk Factors

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

Also, if you are engaged in activities (especially outside) that could cause eye injury, be sure to wear protective eye equipment. Environmental factors can affect people prone to keratoconus and those who are not.

Here are some potential factors to avoid:

  • rubbing the eye: About half of people with keratoconus rub their eyes. This may last for up to 180 seconds, in contrast to the typical five seconds of rubbing in people without this condition. There is some thinking that small trauma to the epithelium from rubbing may contribute to increased inflammation and other activities in the area.
  • sun exposure: Those who live in hot, sunny areas are more likely to develop keratoconus than those in shadier areas. This may be due to the fact that reactive oxygen species can occur due to exposure to ultraviolet radiation.
  • Nicotine use: Cigarette smoking can increase the risk of keratoconus in some cases.

Summary

Having irregular astigmatism can cause blurred vision at all distances. The blurring occurs because the cornea (which focuses light on the back of the eye) cannot shift focus to a single point. With irregular astigmatism, in which the surface of the cornea 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 atrophy that can lead to the development of irregular astigmatism.

Also, lifestyle factors such as eye rubbing, sun exposure, and smoking can play a role in the development of some conditions related to irregular astigmatism.

Word from Verywell

While avoiding irregular astigmatism is best and achievable in some cases, this will not be possible in others. However, paying attention to the possible causes may help reduce the difficulties of this condition.

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

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

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

  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 Liebner

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

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