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What Is Astigmatism & How It Influences Refraction

If you’re one of the one billion people around the world who wear eyeglasses, you probably know just how much a pair of glasses can improve your vision. Some people describe their first time wearing glasses as finally being able to see or like waking up from a deep sleep.

This is especially true for some people with astigmatism. This guide explains astigmatism, including its symptoms, causes, and treatment.

What Is Astigmatism?

If you think back to high school biology, you might remember that eyes are supposed to be spheres. Your ability to see actually depends on your eyeball and cornea having the perfect curvature.

Any changes in the natural shape of the cornea can affect your eye’s refraction, which is an important part of your ability to see. In people with astigmatism, the cornea is either shaped wide like a football or long like the back of a spoon.

This can cause light to bend abnormally in your eye. Instead of one mainstream of light hitting your retina, you might experience two. This can cause things to look blurry and unfocused.

Types of Astigmatism

Normally, astigmatism is specifically caused by an abnormal curvature of the cornea. In this case, you’d have what’s called corneal astigmatism.

However, not everyone has this type of astigmatism. Some people have lenticular astigmatism, which is caused by having an irregularly shaped lens. This condition is also sometimes called irregular astigmatism.

What Is Refraction?

To properly understand astigmatism and how it affects vision, we’ll need to learn how refraction works. There are many complicated things to know about refraction, and we’ll try to keep it as simple as possible — however, the bottom line is that refraction is how our eyes and brains convert light into pictures.

When light hits the eye, the first part it makes contact with is often the cornea. This is a spherical structure that sits on top of the eye. Because of its shape, the cornea bends the light, focusing it enough for the waves to go perfectly through the pupil.

The light immediately goes through the eye’s crystalline lens, which focuses and narrows the light rays to create a tiny pinpoint of light that hits the back of the eye. This pinpoint hits the retina, which activates communication with the brain via a network of nerves. Your brain then interprets these signals as pictures.

Other Refractive Errors

If all of this sounds like the definition of nearsightedness or farsightedness, there’s a reason. Both of these conditions are refractive errors, just like astigmatism.

Myopia, or nearsightedness, occurs when you can’t see objects that are far away. It often happens when the whole eyeball is too long, causing light to refract incorrectly in the eyes.

On the other hand, farsightedness (also called hyperopia) is when you can’t see objects that are close up. This can happen when the entire eyeball is too wide.

Ultimately, the main difference between these eye conditions and astigmatism is that they involve the shape of the whole eye, while astigmatism is usually just based on the shape of the cornea.

How Does Astigmatism Affect Vision?

When you have astigmatism, the corneal surface is either too long or too wide. This can warp light as it passes into the pupil, causing it to split into two streams of light. These two streams hit different spots in the back of the eye, causing multiple focal points. Ultimately, this can lead to vision problems like blurry vision.

What Are the Symptoms of Astigmatism?

The only way to truly know if you have astigmatism is by visiting your eye doctor (more on that later). However, astigmatism can cause some symptoms. If you have any of these symptoms, visiting an eye doctor for an official diagnosis and treatment plan is important.

Common symptoms of astigmatism include:

  • Blurred vision
  • Eye strain
  • Seeing a glare around lights
  • Headaches
  • Squinting
  • In severe cases, amblyopia (lazy eye)

Is Astigmatism Genetic?

You may be wondering what your chances are of developing astigmatism. Unfortunately, there’s one main way to find out: looking at your family tree. One of the biggest causes of astigmatism is genetic factors, just as with other eye conditions like glaucoma. If your parents have astigmatism, it’s likely that you will, too.

Of course, genetics aren’t the only factor. Other risk factors for developing astigmatism include having myopic refraction, being of an Asian ethnicity, environmental factors, eye injury, and eye diseases.

For instance, keratoconus is an eye condition that can cause astigmatism, and pellucid degeneration can also contribute to its development.

How Is Astigmatism Diagnosed?

Even if you have all the symptoms of astigmatism, the only way to know for sure and get treatment is to visit your eye doctor. The symptoms of astigmatism could also indicate other eye issues, and it’s important to know what’s causing your symptoms before looking for possible treatments. This way, you can accurately correct the issue.

Your doctor might want to perform a few tests as part of your eye examination. Here are a few of the most common.

Refraction Test

A refraction test will measure your potential glasses prescription. To do the test, you’ll need to sit in a chair with a refractor attached to it. This device has multiple lenses that can be moved in and out of your vision to help your eye doctor find the best prescription.

You’ll look through the refractor at an eye chart about 20 feet away. Focusing on one eye at a time, your eye doctor will have you let them know how different lenses affect your vision. Your doctor will give you your prescription depending on when your vision blurs or not. Your doctor will also shine a light into your eyes to test your refraction.

Visual Acuity Test

If you’ve ever been to a doctor’s office, you’ve probably at least seen a visual acuity test — even if you didn’t know what it was at the time. This test is when an eye doctor asks you to look at a paper with letters written on it.

The chart will have different lines of letters, each of a different size. The letters get smaller as they descend, and your ability to read each line of letters can indicate whether you need more testing.


This test measures the front (or anterior) curvature of the cornea. With this test, optometrists can figure out the refractive power of your cornea and diagnose refractive disorders like astigmatism. This method can even detect lenticular astigmatism.

The great thing about this test is that the results are objective. This means that patients can’t guess or manipulate the test, so it’s a highly trustworthy way to measure astigmatism.

Slit Lamp Exam

A slit lamp exam is a very common exam that your eye doctor might use to help identify astigmatism. Basically, it helps your doctor see every part of your eye, including inside it.

A slit lamp is essentially a microscope with a light that can be adjusted to reveal different parts of the eye. This test can be used to diagnose many conditions, like cataracts and glaucoma.

How Is Astigmatism Treated?

Once you’ve been diagnosed with an eye condition, your next question will probably be, “what do I do about it?” Luckily, astigmatism can often be corrected with simple techniques and treatment options. If that fails, there are other options available, as well. If you have astigmatism, it’s important to work with an eye doctor to figure out which treatment is best for you.

Corrective Lenses

One of the first steps you can take to correct astigmatism is to wear corrective glasses. Remember, astigmatism is a refractive error like nearsightedness or farsightedness. It can be corrected with specific lenses just like the other errors.

The degree of astigmatism is measured in diopters. You'll likely need corrective lenses if your diopter measurement is above 1.5.

First, your prescription will include a cylinder. This measures exactly how severe your astigmatism is or how tall or wide your cornea is.

Your prescription will also include an axis, which indicates exactly where your astigmatism lies on your cornea. Axis is measured from zero to 180, and it determines where the treatment area is on your lens.

You aren’t limited to frames, either — you can also opt to correct your astigmatism with a pair of contact lenses. Keep in mind, however, that your prescription measurements will be different between frames and contacts.


Orthokeratology is kind of like braces for eyes. This treatment involves using hard contact lenses to guide the cornea into the correct shape.

Unfortunately, the results of orthokeratology aren’t permanent. Unless you wear your contacts every night, the cornea will eventually return to its original shape. However, many people prefer orthokeratology to other options because it’s less invasive than surgery and requires less time than wearing frames or normal contacts.

Refractive Surgery

Lastly, your eye doctor might recommend surgery to physically correct the astigmatism. Many people try to avoid surgery because of the risks and because it can require some downtime. However, it can be incredibly effective in some cases.

Eye surgery procedures like LASIK and PRK can help permanently correct an astigmatism. An ophthalmologist, or eye surgeon, can even add this corrective surgery onto other procedures, like cataract surgery.

Do You Need Special Glasses for Astigmatism?


Many eye doctors also sell prescription glasses frames, so you may be wondering — do you need to buy special frames to correct astigmatism? Luckily, your options are far from limited.

Once you have your eyeglasses prescription, you can purchase glasses from any provider that can cut lenses to match your prescription. This means you can truly shop around for a pair of frames that fit your aesthetic.

But why stop at one simple pair of frames when you can have multiple pairs in one? At Pair Eyewear, we know that your aesthetic can change from day to day, from outfit to outfit. When our personalities shine through in different ways each day, shouldn’t our accessories match?

That’s why we’ve developed our proprietary system of top frames and base frames. Simply select a pair of base frames that fit your personality and face shape. These frames will look just like any other glasses frames, and we’ll fit the lens with your prescription.

Then, you can choose from our massive selection of top frames — or, better yet, try out a couple with our Top Frame Sets. These are magnetic covers that snap on over the face of our bottom frames, allowing for nearly endless combinations. This way, your glasses can be just as fun, quirky, refined, or adventurous as you are.

Can You Prevent Astigmatism?

If astigmatism runs in your family, you might be wondering if there’s any way to prevent it. Unfortunately, there’s not much you can do to preserve your eyesight. That said, the best way to address the possibility of astigmatism is to keep a close eye on your eye care (no pun intended).

For instance, you can schedule regular eye exams to check for astigmatism. If you have young children, it’s doubly important to stay on top of their eye health, since they might not understand the symptoms or know how to communicate what they see.

The Bottom Line

Astigmatism is an incredibly common refractive error. One of the main causes is genetic factors, but it can also be caused by environmental factors and possible eye injuries. Luckily, it can be corrected with glasses and eye surgery.

With a fix as simple as glasses, don’t settle for just one set of everyday frames. Instead, turn your staple accessory into a fashion statement that changes with your style. To learn more about how our system works, visit the Pair Eyewear blog.


Eyeglasses: What They Are, How They Work, Parts & Types | Cleveland Clinic

How the Human Eye Works | Cornea Layers/Role | NKCF

Refraction test Information | Mount Sinai - New York

What Do Astigmatism Measurements Mean? | American Academy of Ophthalmology