What is Astigmatism?

Alongside myopia, hyperopia and presbyopia, astigmatism is one of the most common refractive errors that affect vision. It is an eye condition caused by the curvature being different in different planes for the cornea, lens or both. The British Contact Lens Association (BCLA) defines astigmatism as a ‘focusing disorder of the eye that distorts vision’. If not corrected in time, the quality of vision can get worse. Learn in this detailed guide what causes astigmatism, its various types, symptoms, diagnosis, treatment options and more.

• Types of astigmatism
• What causes astigmatism?
• Symptoms of astigmatism
• Diagnosis of astigmatism
• Treatment for astigmatism
• Vision Simulator Test
• Frequently Asked Questions (FAQs)

Tina Patel, the Contact Lens Optician at Feel Good Contacts, explains what is astigmatism in this YouTube short.

Types of astigmatism

There are mainly two types of astigmatism:

1. Corneal astigmatism: When the cornea is shaped differently to a perfect sphere
2. Lenticular astigmatism: When there’s a distortion in the lens rather than the cornea

Astigmatism can also be described as regular or irregular at times. Regular astigmatism is more common and occurs when the two curves are perpendicular to each other, while irregular astigmatism is less common, wherein the curves are not perpendicular to one another and can be a result of an eye injury or keratoconus.

What causes astigmatism?

Now that you’ve learned what is astigmatism, learning about its causes next would be insightful. A normal eye is shaped round like a football, whilst an astigmatic eye has two different curves, similar to a rugby ball.

Although the exact reason behind what causes astigmatism remains unknown, the following factors can play a pivotal role:

• This refractive error can be present by birth and has been passed down to children from their biological parents.
• Astigmatism can also develop at a later stage of life because of an eye injury, eye surgery or an eye disease.
• Eyelids putting too much pressure on the cornea regularly can cause astigmatism.
• A rare condition known as keratoconus also causes this refractive error by making the cornea thinner and more conical in shape.

Symptoms of astigmatism

Knowing what is astigmatism and how it occurs is not enough; you should also learn about its symptoms so that it can be addressed at the onset and your vision can be prevented from worsening. The symptoms of astigmatism depend on the severity of the condition, which are listed below:

1. Blurred or distorted vision is the most common symptom of this condition, which makes it harder to focus on the details of any object
2. Squinting to see clearly can be an indication of astigmatism
3. Difficulty in seeing at night, because of glare or halos caused by streetlights or car headlights
4. Headache or eyestrain owing to the blurry vision and the pressure on the eyes to focus harder
5. Irritated eyes or discomfort in the eyes
6. Double vision

Diagnosis of astigmatism

An optometrist can diagnose astigmatism through a comprehensive eye test, which may include:

Visual acuity test

This includes reading letters (or symbols sometimes) off a wall chart at a measured distance.

Phoropter

This is a binocular-like device that requires the patient to look through and confirm which letters they can see. This test helps the optician determine the prescription.

Autorefractor

This device provides an initial reading of the prescription and can help measure the astigmatism and other refractive errors.

Keratometer

This device measures the curvature of the cornea, which is essential for the correct fitting of contact lenses.

Treatment for astigmatism

Astigmatism can only be treated surgically by refractive surgery, but it’s best to consult the optician to know if it is a suitable option for an individual. However, it doesn’t always need to be treated and can be corrected by wearing contact lenses or prescription glasses. Here are some of the best options for correcting astigmatism, depending on its severity:

Contact Lenses

Contact lenses are an effective way to correct this refractive error. The optician will recommend toric lenses that are specifically designed to correct astigmatism. Some of the popular contact lenses for astigmatism are:

Prescription Glasses

Prescription glasses are another effective way to correct astigmatism. The optometrist may recommend single-vision, bifocal or progressive glasses, depending on your particular requirement.

Please note: Before opting for any visual correction for astigmatism, it's important to consult your optician to make an informed decision based on the severity of your condition.

Vision Simulator Test

Want to know what does someone with astigmatism see? Try our Vision Simulator Test.

Frequently Asked Questions (FAQs)

What is a bad level of astigmatism?

The term ‘bad level’ of astigmatism is subjective and depends on the severity of this eye condition. Astigmatism is typically measured in dioptres and can be categorised as mild for less than 1.00 dioptres, moderate for 1.00 to 2.00 dioptres, severe for 2.00 to 3.00 dioptres and extreme for more than 3.00 dioptres.

Can you fix astigmatism?

It is unlikely that astigmatism will get fixed naturally. However, it is a good practice to avoid frequent rubbing of the eyes, which could exacerbate astigmatism.

Can you be short-sighted and have astigmatism at the same time?

Yes, you can be short-sighted and have astigmatism at the same time. If you’re unsure, you should get your eyes tested. Your optician will be able to give you an up-to-date prescription and recommend contact lenses and glasses accordingly.

Disclaimer: The advice in this article is for informational purposes only and does not replace medical care or an in-person check-up. Please check with an eyecare professional before purchasing any products or remedies. For information on our article review process, please refer to our Editorial Policy.