The Ultimate Guide to Astigmatism
Medically reviewed by Alastair Lockwood on 26 April 2021
- What is astigmatism?
- What do people with astigmatism see?
- Do people with astigmatism see lights different?
- What makes astigmatism worse?
- What causes astigmatism?
- How to correct astigmatism?
- Are glasses or contacts better for astigmatism?
- Does astigmatism worsen with age?
What is astigmatism?
Astigmatism is an imperfection in the curvature of your eye’s cornea. This hinders your eye’s ability to focus light onto your retina, resulting in blurred and distorted vision. Fortunately, astigmatism is minor and can be corrected easily with toric contact lenses.
Where a normal eye refracts light equally across all of the eye’s ‘meridians’ (imaginary lines across the surface of the eye), an eye with astigmatism means that light will be refracted more in one meridian than the other, distorting the light and the focal point it reaches.
The image below depicts the differences between a normal eye and one with astigmatism. As illustrated, light beams aren’t refracted properly by the astigmatic cornea, resulting in distorted focal points in front of and/or behind the retina.
This translates to blurred and hazy vision, which can also cause general discomfort. If not treated with toric contact lenses or glasses, astigmatism can result in headaches and eye strain.
Astigmatism can be either regular or irregular.
With regular astigmatism, the cornea of your eye is more curved in one particular direction than the other. The principal meridians of your eye are 90 degrees apart, perpendicular to each other.
Irregular astigmatism, however, is when the curvature isn’t even across the eye's surface. It can also be curved in multiple directions or steeper towards the bottom.
Also, astigmatism can be one of three types depending on the visual complications it creates:
- Myopic astigmatism – one or both of the eye’s principal meridians is shortsighted.
- Hyperopic astigmatism – one or both of the eye’s principal meridians is longsighted.
- Mixed astigmatism – one of the eye’s principal meridians is shortsighted, while the other is longsighted.
What do people with astigmatism see?
The two principal meridians of your eye, vertical and horizontal, can have differing effects on the type of vision you experience with astigmatism.
When the vertical meridian is steeper, your vision will be blurry when looking at vertical lines. This is called direct astigmatism.
However, if your horizontal meridian is affected (known as indirect astigmatism), your eyes won’t be able to focus on horizontal lines, again resulting in blurred vision.
What is considered high astigmatism?
A high astigmatism refers to the numbers on your contact lenses or glasses prescription. Generally, the higher the number for the axis and cylinder on your prescription, the stronger your astigmatism is.
The picture below depicts how viewers with severe astigmatism would see.
Do people with astigmatism see lights different?
Depending on how severe a person’s astigmatism is, they may see light differently. Astigmatism means your cornea is shaped like a rugby ball which means light bends in unequal directions and can appear distorted.
The image below shows how someone with astigmatism may see taillights at night compared to someone who doesn’t have astigmatism. Try our vision simulator to see the world through the eyes of someone with astigmatism.
Aside from blurred vision, astigmatism can have a number of other uncomfortable and sometimes painful symptoms.
- Eye strain, particularly behind the eyeballs
- Irritation of the eyes
- Night blindness
Some people may have astigmatism but not experience any of these symptoms. However, it’s important to get your eyes tested regularly to avoid causing unnecessary strain. And, if you experience any of these symptoms, you should visit your optician or GP to see if astigmatism could be the cause.
Why is astigmatism worse at night?
Astigmatism is worse at night or in low light conditions because your eyes dilate in need of more light, increasing the cause of glares, halos, blurry and distorted vision. So, it’s important to check with your eye doctor if it’s safe for you to drive at night, as streetlights and taillights may appear blurred.
What makes astigmatism worse?
If your astigmatism worsens over time, it will happen regardless of whether you wear corrective contact lenses or glasses. There is no strong evidence to prove that myths such as reading in the dark, rubbing your eyes or sitting too close to the television make your astigmatism worse. However, symptoms of astigmatism, including headaches, fatigue, and eye strain, may get worse if left uncorrected.
What causes astigmatism?
There are two types of astigmatism:
- Corneal astigmatism - when the cornea is incorrectly shaped.
- Lenticular astigmatism - when the lens is incorrectly shaped.
With the majority of cases of astigmatism, a person is born with an irregularly shaped cornea or lens, with the eye often resembling more of a rugby ball shape than the typical football shape.
However, there have also been instances of astigmatism developing or becoming more severe later in life. The cause of this is unclear to scientists; however they believe it to be due to genetic factors. If anyone in your family has astigmatism, then you’ll be much more likely to develop it later in life.
Other causes of astigmatism include:
- Eye surgery that changes the corneal surface
- Keratoconus and keratoglobus – eye conditions that change the shape of the cornea
- Conditions that can affect the eyelids such as a large stye or blocked oil gland and that can distort the cornea
Astigmatism is a common eye condition that is easily diagnosed by an optician. This test is done using different methods to evaluate how the eye focuses light.
Firstly, your visual acuity will be measured using a letter chart to determine the clarity of your vision.
Then, your eye's focusing power will be measured with a series of lenses placed in front of them. The lenses that will provide your best vision will be your contact lens/glasses prescription.
Finally, a Keratometer is used to measure the curvature of the cornea, while corneal topography can be used, if required, to provide an even more in-depth study of the surface of your eye.
Before all this, however, you can perform your own astigmatism eye test at home with this helpful picture below.
- If you wear glasses for short or long-sightedness, take them off.
- Sit at a distance of 3 meters from the computer screen and look at the picture.
- First, cover your left eye with your hand and look at the picture with your right eye.
- Repeat with the right eye covered.
- If you see blurred lines or there is a difference in sharpness between horizontal and vertical lines, you might have astigmatism. In this instance, please contact your optometrist or ophthalmologist for further examination.
How to correct astigmatism?
There are three options to correct astigmatism – corrective spectacles, toric contact lenses, and refractive surgery.
Can I wear regular contacts if I have astigmatism?
Besides refractive surgery, which can be very expensive, toric contact lenses are often the most convenient and effective option for correcting astigmatism. They differ from regular contact lenses in that instead of being spherical, they are a torus shape – more similar to a slice of a ring doughnut shape than a slice of a football shape. This allows them to bend and adjust to help your eyes focus on light effectively, therefore offering clearer, undistorted vision.
Another difference between toric contact lenses and regular lenses is that toric lenses contain different powers at different meridians (invisible lines across the diameter) to correct the varying degrees of myopia (short-sightedness) and/or hyperopia (long-sightedness). In most cases, other contact lenses contain one power all the way through the lens. In addition, toric contacts have a design that enables them to rotate into position so that the meridians of power are lined up with the meridians of your eyes that are in need of visual correction.
Toric contact lenses are typically soft contact lenses; however, toric editions of rigid gas permeable lenses can be used to correct irregular astigmatism only. There is also a wide range of toric lenses on the market, meaning that you can find lenses for your wearing needs, whether you’re after daily disposables, two weekly contacts, monthly lenses and, soon, coloured contact lenses.
Are glasses or contacts better for astigmatism?
Both glasses and toric contact lenses effectively correct astigmatism, but generally, contact lenses are preferred. This is because they hold the shape of your eye and are considered more convenient to wear over glasses.
Eye exercises for astigmatism
Unfortunately, you cannot change your eye shape to get rid of your astigmatism through eye exercises.
Does astigmatism worsen with age?
While it’s not always the case, the severity of astigmatism can increase as you age. It’s quite common for direct astigmatism to develop into indirect astigmatism later in life. As our eyelids loosen with age, the pressure that the eyelids usually place on the cornea subsides, resulting in a decrease in the steepness of the vertical meridian curve. In turn, the severity of the horizontal meridian curve increases, resulting in a switch from direct to indirect astigmatism, which can worsen at a gradual rate.
Can astigmatism go away?
Unfortunately, astigmatism cannot simply disappear. Sometimes direct astigmatism can lessen in severity, and it can often go the other way and result in indirect astigmatism. However, as stated above, you can correct your astigmatism with toric contact lenses or opt for a permanent solution with refractive eye surgery.
It's possible to have a mild case of astigmatism and not know about it due to minimal effect on your vision. However, this can lead to headaches, low night vision, eye pain and possibly some blurred vision further down the line. So, if you frequently experience any of these symptoms, pay a visit to your optician.
Quick links:Can you be short-sighted and have astigmatism at the same time?
How do toric contact lenses work?
A guide to blurry vision