Eye Health Resources

Astigmatism: Symptoms, Causes & Treatments

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What is Astigmatism?

One illustrated eye shows a clear letter "s" while an illustrated astigmatic eye shows a blurry "s"

Astigmatism is an eye condition where the shape of your eye is more curved than it should be1. This can cause blurry vision, headaches and eye strain2.

 

While astigmatism may sound complex, it’s actually a fairly common condition that can be treated with glasses or contact lenses2. In fact, it’s estimated that around 50% of people in the UK who wear glasses have some form of astigmatism3.

What Causes Astigmatism?

Astigmatism occurs when a cornea or lens is shaped slightly differently4. It’s not known exactly why this happens, but the risk of developing astigmatism is hereditary, meaning it can be passed down from your parents4.

People can also develop astigmatism as a result of4:

  • Eye injuries
  • Eye disease
  • Problems or complications after eye surgery1.

Contrary to popular belief, reading in low light or sitting too close to the television does not cause astigmatism, nor does it worsen the condition4.

For any questions you have that aren’t answered here, it’s best to reach out to your Eye Care Professional for further advice.

How does Astigmatism Affect Eyesight?

Usually, the cornea and lens at the front of the eye are an evenly round shape4. This helps focus light rays onto the retina so you can see clearly4.

However, for people with astigmatism, the cornea or lens isn’t spherical—it’s more cylindrical, like a rugby ball.

Since light doesn’t pass through a uniform sphere shape, it doesn’t focus equally on one part of the retina (the part of the eye that helps form the images you see). Instead, it focuses on two or more points inside the eye. For example, one point might be on the retina, and one might be behind the retina. This is what creates blurry or distorted vision.

Regular vs. Irregular Astigmatism

There are two types of astigmatism – regular and irregular. Both have slightly different causes and symptoms, so let’s explore each.

Regular Astigmatism

This is the more common type of the two. It occurs when the two curves of the cornea or lens are perpendicular to one another, or, at a 90-degree angle from one another.

Types of regular astigmatism are affected by the orientation of the lens, and include:

  • With-the-rule astigmatism. This is the most common type of regular astigmatism. If we imagine the cornea or lens as a rugby ball, it would be resting flat on the ground. This means that the steeper axis is vertical, and the flatter one is horizontal.
  • Against-the-rule astigmatism. In this instance, the rugby ball would be standing straight up, making the flatter curve vertical and the steeper curve horizontal.
  • Oblique astigmatism. Imagine if the ball was leaning. It would be at an angle, but the two curves would still be perpendicular. For instance, 35 degrees and 115 degrees.

Irregular Astigmatism

Irregular astigmatism occurs when the angle between the curves of your cornea or lens is not 90 degrees. This is often caused by a physical injury.

See Astigmatism Types

Symptoms & effects of astigmatism on eyesight

Uncorrected astigmatism can cause one or more of the following symptoms:

  • Blurry vision at all distances
  • Distorted or squashed images
  • Streaky or haloed lights at night
  • Headaches
  • Eye fatigue
  • Squinting
  • Difficulty seeing at night.

Symptoms can be mild or more severe depending on the shape of your cornea and/or lens. If you are experiencing any of these signs of astigmatism, book an appointment with your optician. They’ll be able to make a diagnosis and give you advice on managing your symptoms.

How can astigmatism distort your vision?

If you have a spherical cornea, light focuses on one place in your eye. If that place is the retina, you’ll probably have clear vision.

However, if your cornea or lens is shaped more like a rugby ball instead of a sphere, light will focus at two (or more) points. Where specifically it focuses can be categorised into the following groups

  • Simple myopic. One of the two focal points is in front of the retina, the other is on the retina itself.
  • Compound myopic. Both focal points are in front of the retina.
  • Mixed. One focal point is in front of the retina, the other is behind the retina.
  • Simple hyperopic. One of the two focal points is behind the retina, the other is on the retina.
  • Compound hyperopic. Both focal points are behind the retina.

Learn more about the effects of astigmatism on night-time vision in our dedicated guide: “Astigmatism and its Impact on Lights and Driving at Night.”

What might someone with astigmatism see?

The image on the left shows an example of a scene with clear vision, and the image on the right shows what the same scene might look like for a person with uncorrected astigmatism.

A side by side image, one for clear good vision, the other for blurry vision with astigmatism.

Astigmatism testing and diagnosis

Astigmatism can be diagnosed by an Eye Care Professional during a comprehensive eye test. The specialist will examine both the exterior and the interior of your eyes to make an accurate diagnosis.

A smiling family of four sits together on a white couch with a bookshelf behind them.

When should I see an Eye Care Professional?

Regular eye tests are essential for detecting vision problems early. Your frequency of eye tests may also vary with age1:

  • Children. Eyesight should be assessed at every child health check-up or visit until they’re old enough to start school. After that, tests should be carried out every one to two years.
  • Adults. At least every two years.

Consult your Eye Care Professional for further advice1.

People who wear glasses, contact lenses, or have certain health conditions such as diabetes may need more frequent tests1.

Moustache man eye exam

How will my Optician check for astigmatism?

Your Optician will usually carry out a comprehensive eye test to determine the shape of your cornea to see whether you have astigmatism. There are a few pieces of equipment they may use to help them:

  • Phoropter. Has various lenses that your optician can use to test your vision and determine your prescription.
  • Autorefractor. Shines a light and measures how the path of the light changes as it bounces off the back of your eye.
  • Keratometer. Measures the curve of your cornea, which can reveal whether it’s round or not.
  • Corneal topography. Maps the shape of your eye. It can help get a precise reading of your astigmatism.

The tests your eye care specialist may carry out include1:

  • Visual Acuity Test. Used to assess how well you can see. This typically involves looking at a wall chart of letters or symbols.
  • Refraction Test. The specialist will measure how light is focused and bent as it enters your eye.
  • Keratometry. Measures the curvature of the cornea.
  • Slit Lamp Exam. A special microscope with a bright light is used to examine different layers and parts of your eye.

Different astigmatism measurements

  • Spherical. Determines whether you are near or farsighted. A plus sign (+) shows you are farsighted, while a minus sign (-) shows you are nearsighted. The higher the number, the stronger the prescription.
  • Cylinder. Measures the degree of astigmatism you have. If your eye is more oval-shaped, you’re likely to have more astigmatism.
  • Axis. Measured in degrees from 0 to 180, referring to the angle of the astigmatism. The 90-degree line runs vertically (north to south) on the eye and the 180-degree line runs horizontally (east to west)4.

Treatment options for astigmatism

Correcting astigmatism so that you can see clearly isn’t a one size fits all approach. Instead, your prescribed solution will depend on your lifestyle, your eyes, and the recommendations from your eye care professional. However, treatment options may include:

Contact lenses

Contact lenses can correct astigmatism by refocusing the light so that you can see more clearly. There are two options:

  • Soft toric contact lenses; designed to correct the specific shape of astigmatic eyes
  • Rigid gas permeable (RGP) lenses. These are often prescribed in more extreme cases of astigmatism.

Glasses

Glasses correct astigmatism in a similar way to contact lenses—by using lenses made specifically to correct your level of astigmatism.

Laser eye surgery

LASIK is a common type of laser eye surgery5 where a surgeon uses a laser to reshape your cornea. As well as helping to correct vision, it can work for many cases of astigmatism too.

Orthokeratology

Orthokeratology is a non-surgical process that involves temporarily reshaping the cornea with specially designed contacts6. These lenses are typically worn at night so that you can experience clear vision during the day without the need for glasses or contact lenses.

If a patient stops wearing the lenses, the corneas return to their original shape and their vision also returns to its original condition.

What happens if astigmatism is left untreated?

Although it’s not often serious, if left untreated, astigmatism can cause some visual issues. This can include a lazy eye, particularly when astigmatism is only present in one eye, or it is worse in one eye than the other and isn’t corrected. Additionally, untreated astigmatism can lead to eye strain and headaches7.

Can astigmatism be prevented?

No, astigmatism cannot be prevented. Most people are born with astigmatism, while others can develop it as their eyes grow and change over time. If parents have astigmatism or another refractive error, there is a possibility that their children may also have it1.

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Astigmatism FAQs

How common is astigmatism?

Astigmatism is a very common eye condition that can cause blurred vision1. It’s estimated that around 50% of people in the UK who wear glasses have some form of astigmatism3.

Do you need glasses for astigmatism?

Most people with astigmatism often need to wear corrective lenses1. However, in mild cases where astigmatism doesn’t affect your vision, this may not be the case1. It’s also worth noting that treatment options for astigmatism can also vary depending on your lifestyle, your eyes and professional recommendations.

Footnotes

  1. ClevelandClinic. Astigmatism. Reviewed 20th November 2022. Available at: https://my.clevelandclinic.org/health/diseases/8576-astigmatism
  2. NHS. Astigmatism. Reviewed 19th September 2024. Available at: https://www.nhs.uk/conditions/astigmatism/
  3. Topdoctors. Astigmatism. Reviewed 12th December 2024. Available at: https://www.topdoctors.co.uk/medical-dictionary/astigmatism
  4. American Academy of Ophthalmology. Astigmatism. Available at: https://www.aao.org/eye-health/astigmatism
  5. Bupa. Laser Eye Surgery. Available at: https://www.bupa.co.uk/health-information/eyes-sight/laser-eye-surgery
  6. WebMD. What is Orthokeratology. Reviewed 8th September 2024. Available at: https://www.webmd.com/eye-health/what-is-orthokeratology
  7. Healthline. What is Astigmatism. Reviewed 26th April 2023. Available at: https://www.healthline.com/health/astigmatism

Consult your Eye Care Professional for more information. Johnson & Johnson does not provide medical advice; this information is for educational purposes only.

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Last updated 18/06/2024
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