Published on: June 18, 2023 || Last Modified: July 21, 2026
By Dr. Kenneth King | Alliance Vision Institute Dr. King is an ophthalmologist at Alliance Vision Institute in Fort Worth, TX.
Astigmatism is the most common reason people wear glasses in the world, and most people who have it do not fully understand what it is. Here is a plain-language explanation of what astigmatism means, what causes it, and what you can do about it.
Astigmatism is not a disease. It is not a condition. It is simply a shape.
Your eye focuses light by bending it through the cornea and lens onto the retina at the back of the eye. For that to work cleanly, the front of the eye needs to be evenly curved, like a perfect sphere. Astigmatism means the front of the eye grew into a shape that is slightly uneven, more curved in one direction than another.
Think of the difference between a basketball and a football. A basketball is symmetrical. Light hits it and bends evenly in all directions. A football has two different curves. Light hitting it bends differently depending on which axis you measure.
When the front of your eye has that uneven curvature, it splits the incoming image into two separate points of focus instead of one. Those two points land at different places, and neither lands precisely on the retina. The result is blur and distortion at all distances, not just near or far.
With nearsightedness or farsightedness, the eye misses the retina in one direction. You can compensate by moving closer or further from what you are looking at.
Astigmatism splits the image. You cannot move to fix it. There is never one clean, focused point anywhere in your visual field. It affects distance, intermediate, and near vision all at once.
That is why people with uncorrected astigmatism often squint. When you squint, you eliminate one of the uneven curves and your brain can find a single focus. It works, but it is a lot of effort for your visual system to do all day long.
A prescription for nearsightedness or farsightedness has one main number, the sphere. A prescription that includes astigmatism has three numbers: the sphere, the cylinder, and the axis. That third number tells the lens maker exactly how to orient the correction so it collapses the two split focal points into one.
Extremely common. Nine out of ten patients who come in for an eye exam have some measurable amount of astigmatism. For most people, the amount is small enough that it does not require correction on its own. For others, it is the primary driver of their glasses or contact lens prescription.
Astigmatism is actually more prevalent worldwide than nearsightedness, though nearsightedness is catching up as screen time increases across populations.
Astigmatism is largely inherited. It tends to run in families, and patients with parents who have significant astigmatism are more likely to have it themselves. It reflects the shape the cornea grew into, and genetics plays a major role in that development.
Eye rubbing can make astigmatism worse. Chronic, forceful rubbing puts mechanical pressure on the cornea and can gradually distort its shape. In more serious cases, this can progress toward a condition called keratoconus, where the cornea becomes increasingly irregular and more difficult to correct.
Yes. This is a common misconception worth clearing up.
Your visual acuity, the 20/20 number, measures how well you can see at a standardized distance. It does not tell you anything about what prescription you need. A person with significant astigmatism who is properly corrected with glasses or contact lenses can see 20/20 with no problem.
Some people with low amounts of uncorrected astigmatism function at 20/20 because the brain learns to interpret the blur over time. It compensates. The patient does not know what sharper vision would look like because they have never experienced it. Put a proper correction in front of those eyes and the difference is immediately obvious.
That is not the glasses making your vision worse. That is your brain no longer willing to do extra work to interpret what it is seeing.
In most cases, no. Astigmatism reflects corneal shape, and that shape does not typically change significantly with age. In some children, the amount can shift slightly as the visual system develops. But outgrowing astigmatism is not something most patients can count on.
What can happen is adaptation. A small amount of uncorrected astigmatism may not feel symptomatic because the visual system adjusts. That is different from the astigmatism going away.
There are more options than most patients realize, and astigmatism is no longer a barrier to surgical vision correction.
Glasses correct astigmatism reliably. The lens is ground to the exact cylinder and axis that collapses the split focus onto the retina.
Contact lenses can correct astigmatism using toric lenses. The word toric simply refers to a lens designed to address astigmatism. Both soft toric lenses and rigid gas permeable lenses are effective options.
LASIK and PRK both correct for astigmatism. The idea that refractive surgery is not an option for people with astigmatism is outdated. There are limits on the amount that can be corrected depending on the system used, but those limits continue to improve with advances in technology.
EVO ICL® (Implantable Collamer® Lens) is an option for higher amounts of astigmatism, particularly when LASIK or PRK is not the right fit. These implantable lenses can address significant astigmatism that falls outside the range of corneal procedures.
For irregular astigmatism, where the corneal shape is more complex and the two focal points are not cleanly 90 degrees apart, specialty contact lenses or customized laser treatment may be required. This is a more nuanced situation, but options exist and are improving.
Not necessarily. The goal of eye care is not to force everyone into correction. It is to make sure you are seeing clearly, comfortably, and efficiently enough to do what your daily life requires.
A small amount of astigmatism that is not causing strain, headaches, or reduced clarity may not need treatment at all. That is a conversation to have with your eye doctor based on your specific prescription and how you are actually functioning.
Astigmatism is a shape variation in the cornea that splits incoming light into two focal points instead of one. It is extremely common, largely inherited, and correctable with glasses, contact lenses, or refractive surgery. It is not a disease, and it is not something to be alarmed by.
If you have been told you have astigmatism and want to understand your correction options, including whether LASIK might be right for you, our team is ready to help. Take our LASIK self-test to get started.
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This blog is part of the Days of Our Eyes series, featuring Dr. Kenneth King and Dr. Christopher Cha at Alliance Vision Institute in Fort Worth, TX.