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Forest through glasses

The Ultimate Guide to Astigmatism

What Is Astigmatism?

Astigmatism is a common condition where the cornea or lens is irregularly shaped. This causes the light entering your eye to be divided into multiple areas, causing blurred vision when looking at objects both near and far.

What Causes Astigmatism?

Astigmatism is part of a group of eye conditions known as refractive errors. Other members of this group include myopia, hypermetropia and presbyopia.

This condition can be described as corneal or lenticular. The corneal kind is the more common of the two, and it simply means your cornea is not perfectly curved. Similarly, if your lens is irregularly curved, it’s referred to as lenticular astigmatism.

While there are many different causes of astigmatism, the most common is heredity. It will often run in the family and be present at birth, developing as you age. Almost all of us have it to some degree, although mild cases of astigmatism may not require treatment.  

What Are The Symptoms of Astigmatism?

Often occurring in tandem with myopia (nearsightedness) or hypermetropia (long-sightedness), the most common symptom is blurred vision, but you may also experience:

  • Headaches
  • Squinting (to focus on text or objects)
  • Eye strain (especially when focusing for long periods of time)

If you are experiencing the above, check in with your optician as it could be linked to another condition.

Regular vs Irregular Astigmatism

There are two types of astigmatism. Limited to just one area on the cornea or lens, regular astigmatism is usually corrected quite easily. It is more common than irregular astigmatism, which is where the cornea is uneven across a number of areas and is usually caused by an eye injury or keratoconus

How Is Astigmatism Treated?

Regular astigmatism can be corrected with glasses or contact lenses, and in some cases, laser eye surgery. The lenses work by bending incoming light rays (to compensate for the underlying refractive error) allowing images to be properly projected onto the retina. The soft lenses used for astigmatism, called toric lenses, are designed to realign your contact lens with every blink, giving you clear and stabilised vision.

Irregular astigmatism can only be corrected with Rigid Gas Permeable (RGP) lenses. They’re thicker than soft contact lenses and their stability provides a rounder shape over the cornea which allows light entering the eye to focus correctly. 

Contact lenses that correct astigmatism are commonly known as ‘toric’ and will have the following specifications:

  • Sphere – a +/- figure that indicates whether you are myopic or hyperopic. It is possible to be neither long nor short-sighted, but still have astigmatism. In this instance, the spherical reading on your prescription will be zero (+0.00)
  • Cylinder – a measurement of how flat or irregular your cornea is shaped.
  • Axis – where on the cornea your astigmatism is located.

Your prescription will typically look like this: -1.00 (Sphere) / -1.25 (Cylinder) x 90 (Axis)

How to Test for Astigmatism

We’ve created a test so that you can see through the eyes of someone with and without astigmatism, but please note that this is not a replacement for a visit to your optician and shouldn’t be used as a diagnosis tool.