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Astigmatism is a common eye condition that affects millions of Americans. The primary symptom is blurry vision, which is caused by improper curvature of the cornea or lens in the eye.
Traditionally, astigmatism is diagnosed via a comprehensive eye exam in an eye doctor’s office. Through three primary vision tests (visual acuity, keratometry, and refraction), doctors can see how light is refracted in your eye and determine if astigmatism is causing your vision problems.
Online or at-home tests have been developed to help people screen themselves for astigmatism. By looking at a series of specific images, you can potentially tell if you likely have astigmatism based on your responses.
Online astigmatism tests are not a replacement for comprehensive diagnostic eye exams, but they can be an accurate screening tool, showing if you potentially have the condition. If the screening indicates astigmatism is likely, then you should follow up with an eye care professional.
Because astigmatism is such a common condition, many effective and affordable treatment options have been developed. Treatments for astigmatism include eyeglasses, contact lenses, and laser surgery options, such as LASIK.
What Is Astigmatism?
Astigmatism is a common eye condition that affects about one in three Americans. It causes blurry vision, and it is often combined with nearsightedness or farsightedness.
When the cornea is misshapen or the lens of the eye is improperly curved, astigmatism can occur. Astigmatism means that light entering the eye is not focused properly on the retina.
Symptoms of astigmatism include:
- Partial blurry vision.
- Blurred vision at all distances.
- Distorted vision.
- Eye strain and discomfort.
- Tired eyes.
Astigmatism is a common vision condition that many people have to some degree. It is usually not the result of disease.
It can be heredity and present at birth, or it can develop over time. Vision conditions, such as pressure, trauma or scarring on the cornea, or vision disorders like keratoconus, can lead to astigmatism. It is also a risk of eye surgery.
How to Test for Astigmatism
Traditionally, astigmatism is diagnosed via a comprehensive eye exam performed by an eye doctor. During such an exam, an eye doctor measures how your eye focuses light.
According to the American Optometry Association, the three primary tests used to determine if you have astigmatism are:
- Visual acuity test. This test is performed by having you read letters on a distance chart. Your results are given as a visual acuity fraction, such as 20/20 or 20/40 vision.
- Keratometry/topography. Through these tests, a keratometer is used to measure the curvature of your cornea. The measurement helps to diagnose astigmatism and determine the proper fit for corrective contact lenses.
- Refraction test. This procedure places a series of lenses in front of your eye to measure how they focus light entering your eye. Focusing power can then be adjusted to determine the degree of astigmatism and the power of corrective lenses needed to help you achieve clear vision.
Online or At-Home Astigmatism Test
If you are concerned that you may have astigmatism, free online tests are available to help you determine whether it’s likely that you do. They do not replace comprehensive eye exams, but these tests can serve as useful screening tools to see if you should follow up with an eye care specialist or not.
One way to check your eyesight for astigmatism at home is by looking at special eye charts. The way you perceive the images on the charts will vary depending on whether you have astigmatism or not.
The astigmatic mirror, as shown below, is an eye chart that can help you screen yourself for astigmatism.
When someone with astigmatism looks at the astigmatic mirror, some of the lines on the image appear darker in certain directions than in others. Typically, someone with astigmatism will see the more horizontal lines more clearly and spaced wider apart than they will be able to see vertically oriented lines.
Another eye chart that can be used to test for astigmatism is pictured below. With this chart, you must position yourself properly in front of your computer screen. Depending on your screen size, position yourself as follows:
- With a 14-inch screen, position yourself about 74 centimeters from the screen.
- With a 15-inch screen, position yourself about 1 meter from the screen.
- With a 17-inch screen, position yourself about 1.5 meters from the screen.
- With a 20-inch screen, position yourself 2.2 meters from the screen.
Once you have positioned yourself properly, look at the following image and follow the steps below:
- Cover one eye with your hand without pressing on the eyelid.
- Look at the image and pay attention to how the lines appear.
- If some lines appear lighter and some appear darker, you likely have astigmatism.
- Repeat the test for both eyes.
An additional series of images designed to test for astigmatism can be found through Prokerla’s astigmatism test. The online test displays images similar to the two above and follows up each image with a yes-no question about how you perceive it. After answering the questions, the test produces a recommendation regarding the likelihood that you have astigmatism and whether you should follow up with an eye care specialist.
How Accurate Are Online Astigmatism Tests?
Online astigmatism tests are helpful for providing an accurate astigmatism screening, but they are not a sufficient replacement for a professionally performed comprehensive eye exam. If you follow the procedures for an at-home test correctly, you can get an accurate self-assessment. This can inform you on your next steps.
Remember these points for at-home testing:
- Each eye must be tested individually.
- Repeat the testing process completely on both eyes.
- Maintain sufficient distance from your testing screen.
- Be sure to note abnormalities in depth and intensity of darkness.
Self-assessment can provide valuable information. Results of online assessments are based primarily on your own judgment, however, so it can be tricky to get objective results. If you are unsure about the results of an online astigmatism test or you think the results clearly indicate that you likely have astigmatism, you should follow up with an eye doctor for an official diagnosis.
Advances in Astigmatism Testing
With the current technological advances, the diagnosis of astigmatism is becoming more accurate. Corneal topography is the latest tool for diagnosing defects of the corneal curvature.
It uses a computer to map out the contour of the front window of your eye, giving a detailed visual illustration of the shape of your cornea. Its ability to detect even the slightest curvature deviations makes it superior to the traditional testing methods.
What if the Astigmatism Tests are Normal?
While astigmatism is a major cause of blurry vision and other associated symptoms, your results on the above tests may all come back normal. That is, you do not have astigmatism.
Now what? More tests. Your doctor will run some other tests such as tonometry, ophthalmoscopy or perform a slit lamp examination to rule out these potential causes of distorted vision.
Several conditions can lead to visual disturbances. Other refractive errors such as nearsightedness and farsightedness could be the culprit. Retinopathy, macular degeneration, optic neuritis, cataracts and retinitis can all cause blurred vision.
No matter how you are diagnosed with astigmatism, there are a number of treatment options available to you, such as:
- Contact lenses.
- Orthokeratology (ortho-k).
- LASIK (laser-assisted in-situ keratomileusis).
- PRK (photorefractive keratectomy).
Even if you use an online test to assess yourself for astigmatism, you will need to see an eye doctor to determine the best treatment options for you. An eye doctor can confirm you have astigmatism and then take additional measurements to fit you with proper eyeglasses or contact lenses, or refer you for an appropriate type of eye surgery.
Fortunately, astigmatism is a common condition with many effective treatment options. Once you are officially diagnosed, it can be easily addressed so you can see clearly.
Astigmatism. American Optometric Association.
Eye Health Statistics. American Academy of Ophthalmology.
Test for Astigmatism. My Eyes.
Prevalence of refractive error in the United States, 1999-2004. (August 2008). Archives of Ophthalmology.
Corneal Topography. (December 2, 2014). American Academy of Ophthalmology.