Astigmatism is a very common condition. Simply explained, it is when the structures inside the eye are not perfectly round, causing light to refract unevenly. This makes your vision blurry and distorted.
In this article, we will go over what is astigmatism, how to determine if you have it, the relationship between astigmatism and myopia, potential causes for this condition and how is it corrected.
Astigmatism Explained Simply
The word astigmatism is from Greek roots: a–“without” + stigma–“point”. It means having no point. In the context of eyesight, it means that the light coming into our eyes does not hit the retina at one point. This makes it so that we do not get a clear image.
Astigmatism is an imperfection in the curvature of the cornea of the eye. It causes light to focus on several points instead of just one point.
The cornea is the front surface of your eye. It protects the inside of your eye from the outside environment and acts as a lens to bend light towards the inside of the eye.
In an ideal world, it is a smooth and perfectly curved surface, making light pass through it in a uniform way. However, most of us have some imperfections in the shape of our cornea. This is what’s called corneal astigmatism.
Light that passes through a cornea with astigmatism will focus irregularly inside the eye. And that causes our vision to be blurry, foggy and even distorted.
Astigmatism can also be caused by anomalies in the shape of the lens inside the eye. When your eye doctor measures your astigmatism, they take into consideration the combination of both corneal and lenticular astigmatism.
Do You Have Astigmatism?
Your eye doctor will tell you if you have astigmatism. You can also know if you have it or not by looking at your eye prescription.
In your eye prescription, look for the numbers next to the following abbreviations:
- CYL: It’s an abbreviation for cylinder and indicates the amout of lens power needed to correct your astigmatism.
- Axis: This is a number between 0 and 180 that represents, in degrees, the angle at which the cornea is irregular.
Generally, the higher the number for the axis and cylinder on your prescription, the stronger your astigmatism is. If these fields are blank, it means you don’t have this condition.
If you’ve noticed your vision tens to be more like the left side of the picture above, it’s probably a good idea to go see your eye doctor.
Astigmatism and Myopia
Astigmatism is different from myopia (nearsightedness), where we do not get a clear image either. But in myopia, it is because the light can only come to a point in front of the retina.
The reason why light can’t focus on one point in astigmatism is that the cornea does not have a regular shape. On the other hand, if you have myopia light can focus on one single point, the problem is it focuses in front of the retina. For clear vision, the light needs to focus exactly on the retina instead.
Now, if you have myopia and astigmatism far away objects will appear blurry (because of myopia) and it might also be difficult to distinguish certain shapes (because of astigmatism).
The symptoms of these two conditions are very similar, as they both result in blurry or distorted vision. It’s very common for people who have myopia to also have astigmatism.
What Causes Astigmatism?
As of today, science can’t answer the question this question with confidence, but genetics are believed to be a factor. Astigmatism is often present at birth, but it may also develop later in life as a result of uneven growth in different parts of the eye.
It can also occur as a result of an injury to the eye or after eye surgery.
More interesting theories suggest it is linked with visual habits. More specifically, because of an uneven use of your eyes. For example:
- Reading lying sideways in bed for long periods of time.
- Sharing a music-stand with someone and always being on the same side of the stand.
- Sharing a textbook in the classroom everyday.
- Uneven lighting during long hours of close-up work.
Basically, if a person spends a lot of time in asymmetric postures, where they have to look to their right more, the left eye should have more astigmatism, and vice-versa.
How Is Astigmatism Corrected?
Mild cases of astigmatism should not require treatment. With that said, your eye doctor can correct it by using one of the following methods.
Both glasses and contact lenses effectively correct astigmatism. However, most people prefer contact lenses because they are more convenient. It’s also common for people who try glasses with an astigmatism correction to complain about distortions in their peripheral vision.
Orthokeratology (Ortho-K) is a treatment where you use a special type of contact lens while sleeping to temporarily correct the irregular curvature of the cornea. This causes your vision to be clear during the day without the need for glasses or contact lenses. Read this article to learn everything you need to know about Ortho-K.
Refractive surgery can also be an option. It involves using lasers to reshape your cornea. This will permanently correct the deformity that is causing myopia, astigmatism, or maybe both. It is advised to read more about the potential side effects before deciding to do the surgery.
Astigmatism is an imperfection in the curvature of the cornea of your eye. This interferes with your eye’s ability to focus light onto the retina, resulting in blurred and distorted vision.
The exact cause isn’t known. Wearing contact lenses or glasses will correct the problem. Your eye doctor might also suggest surgery.
If you suspect you have untreated astigmatism, consult an eye doctor for an eye check-up as soon as possible. If you have any questions, leave them in the comments below!
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