21 January 2020
What causes astigmatism?
Astigmatism is an incredibly common eye condition, affecting almost 50% of British people who wear glasses. It occurs when either the eye’s surface – the cornea – or the lens behind the cornea isn’t as round as it should be. To visualise it, think of an astigmatic eye being shaped more like a rugby ball than a football. The abnormal curvature of the eye distorts any light entering the eye, stopping it from focusing properly on the retina (the back part of the eye that helps you see images). This means that images you receive in an astigmatic eye are blurred and distorted, requiring glasses or contact lenses to correct it.
You can either be born with an irregularly shaped lens or cornea, which is true for the majority of astigmatism cases, or it can develop later in life. Developing astigmatism later in life would usually occur as a result of an eye injury, complications from eye surgery, or an eye disease which changes the shape of your lens or cornea. However, it can also occur due to age-related changes in the eye which, in turn, are usually determined by genetics and are typically unavoidable. Something you probably haven’t considered before is that when your skin loosens with age, the same thing happens to your eyelids. This means that there’s less pressure placed on your corneas, allowing it to curve more and change shape. This is one of the main causes of people’s astigmatism worsening with age.
How do I know if I have astigmatism?
Lots of people don’t actually know that they have astigmatism, especially if they’ve had it since childhood, and have never known anything different. The effects of astigmatism can range from mildly blurry vision to significantly distorted vision. Without effective correction – which we’ll discuss later – astigmatism can lead to:
- Eye pain
- Blurry vision
- Night blindness
- Eye strain
If you’re experiencing any of the above symptoms, you should go for an eye test. Your optician will be able to determine whether or not you’re suffering with astigmatism, and will then recommend new glasses or lenses based on your prescription. It’s important to note that astigmatism isn’t an eye disease or problem with your eye health, but simply a refractive error – much like short- or long-sightedness – and is easily fixed.
How do you test for astigmatism?
The way to find out whether or not you have astigmatism – or any other refractive error – is to book yourself in for an eye test with your optician. You’re particularly at risk of having astigmatism if you have:
- Family history of astigmatism
- A scarred cornea (from surgery or an injury)
- A thin cornea
- High myopia
- High hyperopia
First, you’ll be asked to read letters from a chart to show exactly what you can see unaided. There will also be a refraction test where you read the chart again while looking through lenses of different strengths – determining whether or not these lenses sharpen your vision. Further to these relatively standard eye tests, there is also an examination called a keratometry. This allows the optometrist to measure the curve of your cornea to work out whether there is an irregularity in its shape. Knowing where the irregularities lie on your cornea (or lens) allows effective treatment to be prescribed to correct the blurring caused by astigmatism.
What are the different types of astigmatism?
There are three main types of astigmatism: myopic (short-sighted), hyperopic (long-sighted), and mixed – where a person has different levels of sighted-ness in each eye. Within these categories, there are two further types of astigmatism: regular and irregular. Regular astigmatism is where your cornea is more curved in one direction than another. This is the most common type of astigmatism and, thankfully, it’s easily corrected with glasses or contact lenses. Irregular astigmatism isn’t as common and it’s typically developed later in life. It occurs as a result of Keratoconus or an eye injury, and the curve of the cornea associated with it is uneven. Glasses can’t always rectify the visual issues caused by this, but specialised contact lenses do sometimes help.
Further to these categories of astigmatism are two main types which overarch everything else. Astigmatism can either affect your cornea (corneal astigmatism) or lens (lenticular astigmatism), both of which play a part in bending light onto your retina. Sometimes referred to as external (corneal) or internal (lenticular) astigmatism, The Eye Centre likens the difference to the comparison between a football and rugby ball: “The football has an equal curvature whereas a rugby ball has a difference between the surface curves creating the oblong shape.” The difference in curvature means that you will require different types of corrective contact lenses depending on the cause of your astigmatism.
How can astigmatism be treated?
There are several different methods for treating astigmatism, ranging from simple eyeglasses to laser eye surgery. Depending on your astigmatism prescription, the lenses in your glasses can be made to include some level of correction, reducing the distorted vision. Alternatively, astigmatism can be treated with toric contact lenses, specially designed to bend the light correctly in order to reach your retina in the right place. The shape of them is slightly different to regular contact lenses, as well as correcting for different prescription powers across the lens, if needed.
Some people suffering with astigmatism choose orthokeratology treatment, involving rigid contact lenses to correct imperfections on the cornea. Often, these lenses are worn overnight to change the cornea temporarily, giving the wearer good vision throughout the day. However, the effects don’t last beyond a day or two so orthokeratology is an on-going treatment and the lenses need to be worn at regular intervals over long periods of time.
A permanent solution for astigmatism is laser eye surgery. We offer both LASIK and LASEK here at Optimax, using cool beam lasers to reshape your cornea. As this corrects any irregularities in your corneal curvature, it means that light reaches your retina properly, producing a clearer, sharper image. This change is permanent – unless your prescription is unstable and changes over time – and we also utilise Wavefront technology for an even smoother, more precise finish.
If the astigmatism reading on your prescription is between 1 and 6, it’s likely that you fall within our treatment parameters for permanent astigmatism correction. If your astigmatism reading is between 6 and 8, you could even be suitable for lens implants, using artificial toric lenses to bend the light onto your retina effectively, without the use of contact lenses or glasses. Get in touch on 0800 093 1110 or email email@example.com to find out how we can help.