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If you’re experiencing headaches, blurred vision, eye strain or trouble seeing at night, you may have a common eye condition called astigmatism. Research indicates that astigmatism accounts for roughly 13% of refractive errors (vision problems that make it difficult to see clearly)[1]. The issue, however, is very common in America with approximately one-third of Americans having astigmatism[2].
Astigmatism is caused by an imperfection in the shape of your cornea (the surface layer of your eye ) or lens (an interior part of the eye that helps it to focus) that forms a clear dome in front of the colored part of your eye, the iris. If you’re experiencing vision disturbances that you suspect may be related to the condition, it’s important to seek a professional diagnosis.
Here is what you need to know about the symptoms of astigmatism, its causes and treatment options.
What Is Astigmatism?
Astigmatism is a common condition in which the cornea (the clear window on the surface of the eye) is not perfectly round, says Luke Rebenitsch, M.D., a clinical spokesperson for the American Academy of Ophthalmology and board-certified ophthalmologist and refractive surgeon at ClearSight Center in Oklahoma City.
Normally, the cornea has the same curvature all the way around—it’s shaped like a basketball. Astigmatism causes the cornea to have a flatter curvature along one axis and a steeper curvature along the other; more like a football, explains Dr. Rebenitsch. Horizontal astigmatism occurs when the eye is wider than it is tall, and vertical astigmatism occurs when the eye is taller than it is wide.
“The cornea bends and focuses light that enters the eye onto the retina (the back of the eye), which is translated into an image by our brain,” says Dr. Rebenitsch, adding that if an eye has astigmatism, the light will be defocused, resulting in blurry vision. In short, astigmatism is a type of refractive error (an eye disorder that makes it difficult to see) similar to nearsightedness (myopia) and farsightedness (hyperopia), he says.
How Does Astigmatism Affect Your Vision?
With a round-shaped cornea, light rays are able to focus directly on the retina, allowing for clear vision. But with astigmatism, light rays aren’t able to bend properly to focus directly on the retina. This causes blurry, distorted vision, which may lead to eyestrain, eye discomfort or headaches.
What Causes Astigmatism?
Most astigmatism is genetic, says Dagny Zhu, M.D., an ophthalmologist and refractive surgeon at Nvision Eye Centers in Rowland Heights, California. While she often sees astigmatism run in families, the condition can also be caused by anything that changes the cornea’s shape, including eye surgery and corneal scarring from trauma or infection. In individuals who are genetically predisposed, rubbing the eyes frequently can also cause astigmatism, adds Dr. Rebenitsch.
Keratoconus, a common disease of the corneal collagen, can cause a type of astigmatism called irregular astigmatism, says Dr. Zhu. With keratoconus, the cornea becomes weak, bulges outward (creating a cone shape), and becomes steeper over time, leading to increasing nearsightedness and astigmatism, she says.
Types of Astigmatism
There are two types of astigmatism–corneal and lenticular, says Dr. Rebenitsch, noting that both types are most often experienced as blurry or distorted vision.
Corneal Astigmatism
Corneal astigmatism occurs when the cornea is curved more in one direction than in the other, says Dr. Rebenitsch.
Lenticular Astigmatism
Lenticular astigmatism happens when the part of the eye that is misshaped is the lens rather than the cornea, says Dr. Rebenitsch.
Regular Versus Irregular Astigmatism
According to Dr. Rebenitsch, regular astigmatism, in which the eye is evenly curved, or misshaped, is much more common than irregular astigmatism, in which the eye is curved unevenly.
Symptoms of Astigmatism
Astigmatism usually occurs in conjunction with myopia (nearsightedness) or hyperopia (farsightedness), but can occur on its own as well, says Yuna Rapoport, M.D., a board-certified ophthalmologist, founder and director at Manhattan Eye in New York. Symptoms can include:
- Blurry or distorted vision, especially at night
- Eyestrain
- Headaches
- Needing to squint to see clearly
- Eye discomfort
While all objects appear blurry with astigmatism, what’s most noticeable is the distortion of light that happens at night, says Dr. Zhu. “Instead of pinpoint lights, traffic lights may look like long streaks and starbursts. You may also notice halos and glare around lights at night,” she says, adding that many people with astigmatism have difficulty driving at night as a result.
Experiencing astigmatism symptoms doesn’t automatically mean you have the condition; it’s best to schedule an eye exam for a diagnosis, adds Dr. Rebenitsch.
What Does Astigmatism Look Like?
Rather than having a round, basketball-shaped cornea, individuals with astigmatism will have an abnormal, football-shaped cornea. Because of this, the eye is unable to focus light rays to a single, focused point, leading to blurry or distorted vision.
Risk Factors for Astigmatism
According to Dr. Rebenitsch, risk factors for astigmatism include:
- Genetics
- Other ocular diseases (like farsightedness and nearsightedness)
- Previous eye surgeries or eye injuries
- Changes to the lens that occur with aging
- Keratoconus
Who Is Most At-Risk for Astigmatism?
While the cause of astigmatism is unknown, it is usually present at birth in individuals with the condition. Astigmatism may develop following an injury or surgery, such as cataract surgery. Additionally, astigmatism often co-occurs with nearsightedness or farsightedness.
Keratoconus, an eye disease that affects the shape of the cornea, may also lead to astigmatism. With keratoconus, the shape of the cornea gradually changes from a round shape to a cone shape, leading to vision problems over time.
Astigmatism Tests and Diagnosis
Symptoms of astigmatism can be similar to other refractive errors, so it’s important to see an eye care professional for an exam, says Dr. Rebenitsch, adding that your doctor may perform tests, including:
- Reading letters on an eye chart to determine the sharpness of your vision at various distances, called a visual acuity assessment test.
- Looking through a phoropter (a binocular-like machine) to identify which letter you see better.
- Shining a light into your eye to see how it changes as it bounces off the back of your eye with a device called an autorefractor.
- Measuring the curve of your cornea with a keratometer.
In addition, eye care professionals can take a map of the eye called a corneal topography that measures the curvature of the cornea in order to measure astigmatism, says Dr. Rebenitsch.
Astigmatism Treatments
Mild instances of regular astigmatism do not require correction as long as you’re able to see well, says Dr. Zhu, but blurry vision will occur if more severe cases of astigmatism are untreated. And irregular astigmatism caused by a progressive disease like keratoconus should be treated right away, he says—that’s because it can worsen over time, making treatment more difficult.
In cases of regular astigmatism, prescription eyeglasses or contact lenses work by refocusing light on the retina to improve vision, says Dr. Rebenitsch. You may be a candidate for corrective surgery, such as LASIK or lens replacement depending on your age and eye anatomy, he says.
Irregular astigmatism is not typically correctable with glasses, regular soft contact lenses or traditional laser eye surgery like LASIK, explains Dr. Zhu. It usually requires a special hard contact lens to restore vision called an RGP or rigid gas permeable lens. In some cases, a special type of laser eye surgery (topography-guided PRK) can fix irregular astigmatism by reshaping the cornea, she says.
If you have been diagnosed with astigmatism, your ophthalmologist can help you decide the best course of treatment. If you’re experiencing blurry or distorted vision as a result of the condition, it can typically be corrected with prescription eyeglasses, contact lenses or surgery, assures Dr. Rebenitsch.
Is LASIK Worth It for Astigmatism?
LASIK, or Laser-Assisted In Situ Keratomileusis, is a procedure in which your ophthalmologist uses a laser to permanently change the shape of your cornea. By reshaping the cornea, light rays are able to focus properly on the retina. The average cost of LASIK in 2020 in the U.S. was $2,632 per eye, according to a 2021 report in Clinical Ophthalmology[3]. Speak with your ophthalmologist to determine if LASIK is the best course of treatment for you.
How to Prevent Astigmatism
Unfortunately, there is no way to prevent astigmatism. However, many treatment options are available, including eyeglasses, contact lenses and corrective surgeries such as LASIK and PRK.
When to See an Eye Care Specialist About Astigmatism Symptoms
If you’re experiencing symptoms associated with astigmatism, such as blurry or distorted vision, eyestrain, headaches or squinting to see clearly, an eye care specialist can perform a standard eye exam with a refraction test to determine the cause of your symptoms. Contact your eye care specialist if vision problems worsen or do not improve with glasses or contact lenses.
Frequently Asked Questions (FAQs)
How common is astigmatism?
Astigmatism is a common vision condition that affects approximately one out of three people in the U.S.
How do people with astigmatism see lights?
With astigmatism, you may notice a distortion of light that is worsened at night. Traffic lights may appear as long streaks and starbursts, and you may notice halos and glare around lights. As a result, many individuals with astigmatism have difficulty driving at night.
Can glasses fix astigmatism?
Eyeglasses are an effective treatment to correct astigmatism, but do not cure the condition. Speak with an eye care specialist about treatment options for astigmatism.
What causes astigmatism to worsen?
Keratoconus, a condition in which the shape of the cornea changes from a round shape to abnormal, cone shape, may cause astigmatism to worsen over time. Cataract surgery may also worsen astigmatism, as the shape of the cornea may change following the procedure.