Is Astigmatism Dangerous?

Is Astigmatism Dangerous?

Astigmatism can blur your vision. This in itself is frustrating to deal with. But with astigmatism, do you have to also be concerned that it will cause you to go blind in the future? For most people, the answer is no.

Astigmatism generally is not dangerous. Most commonly, astigmatism in your vision can be corrected with glasses and / or contact lenses. However, there are times when astigmatism can be dangerous and lead to vision loss.

So how can you tell whether your astigmatism will cause a problem. There are a few key differences between standard astigmatism and the threatening type.

The non-threatening type of astigmatism

Astigmatism is actually quite common. Over 45% of adults in the United States have astigmatism.

When you have astigmatism, your cornea isn’t a perfect dome. One direction of the cornea is steeper than the other direction. This creates a shape more like a football.

Untreated, astigmatism will blur vision. Light that enters the steep part of the cornea focuses at a different point from light that enters the flatter part. Because those two points of light aren’t focused together, this creates a blur. The greater the difference between the steep part and the flat part, the greater the amount of astigmatism and the greater the blur.

Blur from vertical and horizontal astigmatism

Blur from vertical and horizontal astigmatism, image by English: The original uploader was Tallfred at English Wikipedia. Português: O uploader original foi Tallfred em en.wikipedia, BSD, via Wikimedia Commons / cropped from original

The important point to note about most types of astigmatism is that it is regular. Regular astigmatism is the same in both directions - it’s symmetric. If the top part of the cornea is steep, the bottom part of the cornea is also steep by the same amount. This symmetry allows normal regular astigmatism to be corrected with glasses and contact lenses.

When can astigmatism be dangerous

There are two main conditions in which astigmatism can cause you to permanently lose vision. In these situations, it’s important to see an eye doctor to be evaluated.

Signs your astigmatism could be dangerous:

  • Your astigmatism keeps getting worse every year. Typically, the astigmatism in your vision remains stable from year over year. While you may have small changes that require a few tweaks in your glasses, these changes generally don’t get worse and worse over time.
  • Your vision doesn’t correct to 20/20. Especially if your vision used to correct to 20/20 (see also What Does 20/20 Vision Mean?). While there may be other reasons why you can’t see 20/20, if it’s caused by your astigmatism, this is dangerous to your vision.

Irregular astigmatism & keratoconus

With normal astigmatism, we talked about the astigmatism being regular and symmetric. Irregular astigmatism is the opposite. It is asymmetric. This astigmatism cannot be corrected with standard glasses or contact lenses.

Irregular astigmatism may be a result of something: such as trauma to the eye. In those cases, the irregular astigmatism technically isn’t dangerous - that prior trauma isn’t expected to get worse after it’s all healed. But in some cases, irregular astigmatism can be a sign that you are losing vision. This is the case with keratoconus.

Keratoconus is a condition which causes progressive weakening of the cornea. Over time, the weak cornea changes shape, blurring and distorting your vision. If left untreated, keratoconus can cause you to go blind.

As the cornea changes from keratoconus, it first causes your astigmatism to progressively increase. The astigmatism can also flip directions as it worsens. As the keratoconus progresses, the cornea changes from a dome shape into a cone shape. This causes the astigmatism to become irregular. This irregular astigmatism will cause you to lose vision.

Learn more about how things change at Breaking Down The Stages Of Keratoconus & What You Experience.

Treating dangerous astigmatism

Irregular astigmatism can be corrected, it just takes special contact lenses. The only way to treat irregular astigmatism is by changing the shape of the surface of the cornea. You have to get rid of the asymmetry. Soft contact lenses won’t work, these lenses just conform to the irregular cone shape on the cornea. Hard contact lenses are the only option.

There are two different types of hard contact lenses: rigid glass permeable contact lenses and the newer scleral contact lenses. As the name describes, these lenses are hard. When these lenses are placed on the cornea, the lens still retains it’s dome shape. It essentially converts the cone shape on the cornea back into a dome shape again. These can dramatically improve vision in keratoconus.

But before treating the vision, it is important to make sure that the keratoconus isn’t getting worse. To prevent the keratoconus from getting worse, a procedure called corneal cross-linking is performed. This procedure strengthens the cornea to prevent further weakening. This can prevent you from going blind from the keratoconus or needing major surgeries such as a corneal transplant. While it can’t eliminate the irregular astigmatism, it is an essential procedure when the keratoconus is first diagnosed.

Astigmatism is dangerous for children

As kids grow into adolescents and teenagers, they are constantly developing. The same is true for their eyes and their vision. It is not until kids are about 12 years of age that their vision is fully developed. In the meantime, anything that effects their vision can permanently prevent their vision from developing.

Astigmatism is one condition which can prevent vision from developing in children. Poor development of vision is called ambylopia or lazy eye. The higher the amount of astigmatism, the more dangerous it can be.

But, you can prevent ambylopia; even with high amounts of astigmatism. Ambylopia develops when the eye isn’t seeing anything in focus. Astigmatism causes amblyopia because it causes everything to be blurry. But if you correct the astigmatism with glasses and sharpen up the vision, you can prevent amblyopia from occurring. If you treat the astigmatism early enough, you can even reverse the amblyopia.


The vast majority of individuals need not worry if their astigmatism is going to cause loss of vision. However, sometimes astigmatism is dangerous. The irregular astigmatism caused by keratoconus will cause you to lose vision and if left untreated can cause you to go blind. In children, untreated astigmatism can cause poor development of vision. These dangerous types of astigmatism must be treated to keep the eyes healthy and the vision good.

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