If you have astigmatism, it means that there is a problem with how light focuses on the back of the eye, due to the irregular shape of the cornea or lens. Astigmatism is not an eye disease but is known as a refractive error. We are able to see because of the way our eyes bend (refract) light, which then travels to the brain as information and forms an image. People with astigmatism aren’t able to focus light equally on the retina, which causes blurry vision.

If you have astigmatism and are considering contact lenses, the type of astigmatism you have will determine which lens is best for you. An optician can tell you what kind of contact lenses you need and ensure they are well-fitted to the shape of your eyes. Wearing the wrong type of contact lenses with an outdated prescription or incorrect fitting can lead to blurry vision, discomfort, and an increased risk of eye damage and infections. 1

Myopic astigmatism

Myopia (short-sightedness) is a refractive error, meaning there is a problem with focusing light accurately onto the retina. This makes it difficult to see objects at a distance, such as the TV or road signs.

Myopic astigmatism is a condition in which one or both meridians in the eye are myopic. This means that the light rays are brought to focus in front of the retina instead of on the retina. When both meridians are myopic, there is a differing degree of near-sightedness in each.

Before we continue, it’ll be useful to quickly define what a ‘meridian’ is. First, in an eye test you’ll often be asked to focus on one object or point. If you now imagine your eye to be inside a sphere, with your pupil being at the very centre of it, a meridian is a part of that sphere that goes from above your fixation point to down below it.

So, when someone has both myopia and astigmatism, the blurring of vision caused by the myopia is made more noticeable by the blurring caused by astigmatism. It is not possible to distinguish the individual effect of each condition, so if a person who has both conditions wears contact lenses that only correct myopia, their vision will still be affected by their astigmatism.

This means that simply wearing soft contact lenses with the appropriate negative power for myopia is not enough to correct blurry vision, and either gas permeable or toric contact lenses will be needed to correct both problems. Toric contact lenses are made to specifically correct vision for astigmatism and are designed to stay properly oriented on the cornea.

Hyperopic astigmatism

Hyperopia (long-sightedness) is another refractive error in which the light rays focus behind the retina instead of on the retina. This makes it difficult to see objects up close, such as a book or computer screen.

Hyperopic astigmatism is a condition in which one or both eye meridians are long-sighted — and when both meridians are affected, there is a different degree of hyperopia in each.

When someone has both hyperopia and astigmatism, they need cylindrical lenses to correct the astigmatism (soft lenses called Toric lenses are often used here), and aso spherical lenses to correct the hyperopia. Toric lenses are available in a range of plus powers for people with both hyperopia and astigmatism.

Presbyopic astigmatism

Presbyopia is an age-related condition in which the lens loses flexibility. It typically occurs at around age 40 and means that you may find it difficult to look at objects that are close by.

Presbyopia and astigmatism can occur together and both are very common. Multifocal toric contact lenses are a good option for people with presbyopia and astigmatism, as they have distinct fields that allow you to see up-close, in-between, and far away.

Mixed astigmatism

When one meridian is myopic and the other is hyperopic, it is called mixed astigmatism.

Every individual with astigmatism is unique. Only an optometrist or eye doctor can determine the amount and type of astigmatism present in your eyes. The type of contact lenses prescribed to you will depend on the shape of your eye, the type of astigmatism you have, and whether you have any co-existing conditions such as being short-sighted.

Visit the Specsavers astigmatism page to learn more about astigmatism as a condition. You can find more information regarding astigmatism and contact lenses  here and the contact lens options available to you, or book in a chat with one of our friendly Specsavers optometrists. For more information regarding wearing contact lenses with other eye conditions, you can learn more in our dedicated resource.

References
  1. Livestrong. (no date). The Effects of Wearing Wrong Prescription Contacts. [Online]. Available at: https://www.livestrong.com/article/193947-the-effects-of-wearing-wrong-prescription-contacts/ [Accessed 27 September 2019].
  2. The Free Dictionary. (no date). Hypermetropic Astigmatism. [Online]. Available at: https://medical-dictionary.thefreedictionary.com/hypermetropic+astigmatism [Accessed 27 September 2019].