February 8, 2022 | Basecamp

The Astigmatism Risk Factors You Want To Know About

By Barrett Eubanks, M.D.

The Astigmatism Risk Factors You Want To Know About

Astigmatism can cause vision to be quite blurry. While this can be corrected with glasses, it still would be nice to avoid getting any astigmatism as much as possible. So what are the risk factors for astigmatism and how can one prevent it from developing?

The vast majority of astigmatism doesn’t have any particular risk factors (at least that you can change). But there are certain ways that astigmatism can be acquired. Pterygiums, styes and eye surgery are conditions that can cause astigmatism. Avoiding those risk factors can prevent astigmatism from developing.

While there are some steps to take to prevent some of these types of astigmatism, many others you don’t have much control over.

Background on astigmatism

Astigmatism causes blurry vision. It is similar to nearsightedness and farsightedness in that astigmatism can be corrected with glasses. All of these three conditions share the same issue - light isn’t focused onto the retina.

With astigmatism in particular, the cornea isn’t shaped like a perfect sphere. The cornea is shaped more like a football. One direction of the cornea is steeper than the other direction of the cornea. Because of this, light entering our eye isn’t all focused together. Light that enters the steep part of the cornea is focused at a different point than light that enters the flat part of our cornea. Because the light doesn’t at a single point onto the retina, you get blurry vision.

Where does astigmatism come from

When we are born, we have very high amounts of astigmatism. That is, within the first few months of life. But over the course of the first few years of our life, this corrects itself and the astigmatism goes away. At least for most people.

Within childhood, some kids will still have some astigmatism remaining.

We don’t know everything about what exactly causes astigmatism for everyone, but many things have been looked at. There are some known risk factors for developing astigmatism.

  • There may be a small genetic component to astigmatism. While this genetic relationship isn’t 100%, you may have a slightly higher chance of having astigmatism if your mother or father has astigmatism.
  • Astigmatism happens more often in certain ethnicities. In particular, East Asians and Native Americans are especially known to have a higher rate of astigmatism. Hispanics can also have more than the average population.
  • How the eyelid sits on the eye and cornea can influence whether and how much astigmatism develops. Eyelids that sit too tight onto the cornea can compress the cornea and cause the top and the bottom to steepen - causing astigmatism. Gradually as we age and our eyelids become less tight, our astigmatism can change as a result.

In these cases, you are either born to develop astigmatism or you are not.

Acquiring astigmatism

But despite being born with healthy eyes, there are a few things that can cause astigmatism. And sometimes these things can cause very high amounts!


Pterygium; image by Wilfredor, CC BY-SA 4.0, via Wikimedia Commons

A pterygium [pronounced: tr - i - jee - uhm ] is a growth that can occur from the conjunctiva (the white part of the eye) onto the cornea (the clear part of the eye). As the ptergyium grows onto the cornea, it causes flattening. Because this flattening of the cornea only occurs where the pterygium is and not in other directions, this leads to astigmatism.

As the pterygium continues to grow onto the cornea, the flattening becomes more profound and the astigmatism gets worse. Before the pterygium grows too much and causes too much astigmatism, pterygiums should be removed. This is done through a simple surgery to cut off the pterygium from the surface of the cornea.

But we obviously want to avoid pterygiums as much as possible, so how can we prevent them from growing? Pterygiums occur due to chronic exposure and irritation from being outside. Dust, wind and UV light from the sun all contribute to the growth of pterygiums.

The best way to prevent pterygiums from getting worse, then, is to limit the exposure of the eyes outdoors. Whenever you go outside, it’s important to wear sunglasses to protect the eyes. This is especially important if your job is outdoors or if you live in an especially sunny or dry location.

Changes in your eyelid position

As discussed, the position of your eyelid against your eye and cornea can cause astigmatism. While this is something you typically can’t control, there are times where this can change and cause astigmatism. In fact, when you are looking down and reading something for a prolonged period of time, your eyelid will push in on your cornea more and cause a temporary increase in astigmatism! But there are other conditions (and eyelid surgeries) which can change the way the eyelid interacts with your eye and increase the amount of astigmatism you have.

If you develop a stye or chalazion of the eye, your eyelid changes. Our eyelids contain oil glands called meibomian glands. These glands secrete these oils onto the surface of our tear film to protect our eyes from drying out. If these oil glands become clogged, the oils have nowhere to go and form a bump in the eyelids. This is a chalazion. If this gets infected from normal skin bacteria, it becomes known as a stye.

Eyelid Stye
Eyelid Stye; image by Andre Riemann, Public domain, via Wikimedia Commons

The bump that a stye creates in the eyelid puts extra pressure on the cornea. You may have guessed it at this point, but this extra pressure can steepen the cornea and cause astigmatism in your vision. But fortunately, as you treat the stye with warm compresses and omega-3 supplements (or need to have a procedure to drain and resolve the stye), the cornea reverts back to your normal and the extra astigmatism goes away.

How can you prevent styes from developing? Well, there is no fool-proof way to prevent them. But if you suffer from frequent styes, using warm compresses (which is a heated pad on the eyelid to warm and liquify the oils) and taking omega-3 supplements (which allow for the production of smoother thinner oils) can help to prevent styes from developing in the future.

Eye surgery and / or injuries

One last major cause of acquired astigmatism is as a result of eye surgery or trauma to the eye that needs eye surgery. There are a few surgeries known in particular to cause astigmatism. A particular surgery for retinal detachments called a scleral buckle can cause short-term changes in astigmatism. Any surgery involving the cornea such as a corneal transplant can cause a very large amount of astigmatism. This includes surgery to repair trauma to the eye.

In many cases, there isn’t a whole lot you can do to avoid having eye surgery. Sometimes you just need it. For example, If you are highly nearsighted, you are at a greater risk of having a retinal detachment and needing a scleral buckle surgery for repair.

But you can mostly avoid eye trauma. If you work near objects that can become projectiles, you should be wearing safety goggles. This applies at home as well. Activities such as moving the lawn can fly all sorts of sticks and rocks at your eyes. Wearing safety goggles can protect your eyes and prevent needing eye surgery.


With astigmatism, you mostly have it or you don’t. There may be a weak genetic link and certain ethnicities are more likely to have astigmatism than others. But there are a few ways you can try to prevent developing astigmatism from some other cause. Protecting your eyes from pterygiums and injuries and treating styes can all reduce your risk of getting astigmatism.

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