Astigmatism is a very common refractive defect where light is incorrectly focused inside your eye thus creating, a 'scattering'. The main cause of astigmatism is due to an uneven curvature in the cornea or sometimes in the lens of the eye. This uneven curvature of the eye can bend enter light irregularly, which affects your vision at all distances.
Around the world, more than 33% of people are affected by this. The symptoms are blurry vision, headache, and difficulty reading. Some individuals are born with it, and others develop it later in life. What should you do to avoid it?
Anyone can cure it just by wearing glasses on their eyes. But there are multiple other ways to get treatment for it.
What is the main cause of astigmatism?
The main cause of astigmatism is distinguished by an asymmetry in the cornea or the crystalline lens.A normal eye shape is round like a baseball, but in astigmatism, your eyes should be more like a rugby ball.
This means the eye is shaped more like a rugby ball than say a soccer ball and effects how light is refracted (bent) towards the retina within the eye.
Here's an illustration of what this means.
In many cases, Astigmatism is considered as a genetic trait inherited from your parents, accounting for 47% of UK children and adults. Astigmatism is a very common condition and is typically more predominant in one eye than the other.
This can also be caused due to adding pressure on the eyes, injuries, and sometimes after the completion of an eye surgery.
Astigmatism isn’t caused by reading in poor light, sitting too close to the television, or squinting.
Keratoconus (progressive eye disease) also causes the cornea to thin and bulge into a cone shape that leads to severe astigmatism.
Comparatively, other bodily characteristics such as the ears and nose are equally as likely to be asymmetric.
Typical astigmatism symptoms
There are a few common ways to identify these symptoms.
- Blurry or distorted vision at various distances.
- Squinting to read.
- Difficulty seeing at night.
- Eye strain.
- Headaches
Note: These symptoms can also be caused by other vision problems, which means it's mandatory to get a comprehensive eye exam from an ophthalmologist to confirm the diagnosis.
What Tests Are Used to Diagnose Astigmatism?
There are multiple ways to find out this Astigmatism. During your eye test, your optometrist will go through a series of ocular assessments.
Retinoscopy Test To Degnose Eyes
The primary test for astigmatism is retinoscopy(a device that shines light). This technique is used to detect reflective error in your eyes, including astigmatism, nearsightedness (myopia), and farsightedness (hyperopia).
To perform this test, your optometrist uses a device called a phoropter. This instrument contains a carousel of optical lenses which are placed over your eyes in front of a bright light. As the light is shone into your eye through the various phoropter-lenses, the optometrist can establish if you have any refractive defects in your eye-lens or cornea.
Phoropter Test: The optometrist will switch between lenses or angles and ask which one looks clearer to you. Here, you had to read the chart on the wall, and your answers will help to identify your lens strength that suits your eyes.
Keratometer: This tool uses a corneal topography scan to identify the curve of your cornea. This scan will provide a detailed map of your cornea to spot any irregular shapes or surface issues.
How do glasses correct astigmatism?
On your prescription paper, you'll see two neighbouring sections called CYL and AXIS for each eye. Together, these corresponding values use dioptric power, tilted at a specific angle to compensate for your astigmatism.
Here's a breakdown.
CYL denotes your required cylindrical correction in your lenses to correct your misshapen cornea. This is measured in dioptres so the higher the CYL, the more astigmatic your eye is.
E.g. +2.25, -0.50 or +1.75
Directly after, you'll see a corresponding box called AXIS. This is measured as an angle which compensates for the asymmetry in your cornea. Depending on your specific astigmatism, this angle can be anywhere within 180 degrees.
Eg: 090, 120, 010
Astigmatism may be present in just one or both of your eyes. If you have a cylindrical power for either eye, you will always see a follow AXIS value.
If your prescription doesn't state any cylindrical power, you won't have any AXIS angle and therefore do not have astigmatism in that eye.
Can astigmatism be cured?
Astigmatism cannot be cured; however, it can be optically rectified in three different ways: via contact lenses, prescription glasses, or refractive surgery.
Good quality eyeglasses are by far the simplest solution for an astigmatism cure. Generally, prescription glasses are the most popular solution as they are less difficult to wear than contact lenses and less costly than refractive surgery.
Refractive surgery is also a great option to correct vision for a lifetime. This could be quite expensive, but this is a one-time solution without any side effects.
Astigmatism shouldn’t necessarily be viewed as ‘curable’ as asymmetry is present is many other bodily aspects. This refractive issue is a structural defect and shouldn’t be considered a disease or transmissible condition.
Good quality eyeglasses are by far the simplest solution for an astigmatism cure.
How do things look with astigmatism?
If your astigmatic, your vision may be blurry, fuzzy or distorted depending on what you're trying to observe or read. This can make it hard to focus properly, making you squint or strain whilst trying see.
This is by no means your fault and is simply a hugely prevalent refractive defect within your eyes. As the light passes through your cornea, it becomes distorted from improper refraction.
This scatters the light before it reaches the retina at the back of your eye which creates an imperfect retinal signal. This signal is then passed on to the brain giving a poor interpretation of what is in front of you.
Astigmatism glasses are a good way to resolve this issue by correcting this refractive defect. Lenses with a CYL and relative AXIS will compensate for the asymmetry in your cornea.
How Do Eye Doctors Write Astigmatism in a Prescription?
Optical power or prescription of Astigmatism is measured in diopters. A clear vision means 0 diopters. Each prescription describes the shape of your lens, which includes Spherical, Cylindrical, and axis.
Here, the spherical lens indicates the lens power needed to correct nearsightedness or farsightedness, whereas the cylindrical part is used to indicate the degree or extent of the irregularity. Both are measured in diopters that can be positive or negative.
Finally, the axis is used to define the angle of the placement of the cylindrical lens.
What causes astigmatism to worsen?
Unfortunately, astigmatism is known to change throughout your life and can deteriorate with age. Unusual injuries to the eye such as blunt trauma or the disease keratoconus are known to induce or worsen astigmatism. These are generally the only external circumstances that can make this eye condition worse.
There are various myths that surround astigmatism, one of which concerns whether or not wearing your glasses can have a negative effect. This myth is simply not true and has no detrimental influence at all.
Other myths include squinting too often or reading in poorly lit environments. Neither of these can cause astigmatism to worsen and are more likely to be a cause of eyestrain or headaches.
Key takeaways
- Astigmatism is a very common eye condition caused by a refractive defect in the eye, distorting light before it reaches the retina.
- Corrective CYL dioptres and relative AXIS can alleviate this refractive defect.
- Astigmatism may worsen throughout your life and generally deteriorates with age.
- External factors, such as blunt trauma to the eye or diseases like keratoconus, can induce or worsen astigmatism.
- Myths exist about wearing glasses, squinting, or reading in poor light causing astigmatism to worsen. These myths, however, are unfounded.
Ultimately, the best advice to combat astigmatism is to wear correctly prescribed eyeglasses.
By default, it's far more comfortable to wear your prescription glasses to improve daily visual tasks. Activities such as reading, writing, driving, and watching TV are much easier if you can see correctly.
Hopefully, you found this article helpful. Please check out our other eyecare blogs. Thanks for stopping by.