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Testing for Astigmatism and What Comes Next
A comprehensive eye exam is the gold standard for testing for astigmatism, which is an irregular curvature of the eye’s cornea or lens. Your doctor will perform a series of examinations, including visual acuity, refraction and keratometry, to determine how your eyes focus light on the retina.
Astigmatism is a common refractive eyesight error, affecting up to a third of Americans. Most people who have astigmatism do not experience any symptoms because their condition is so mild. If you have blurry vision with eye strain or headaches, astigmatism could be the cause.
Because blurry vision can occur in several other eye conditions, comprehensive testing in a doctor’s office is the best way to determine if you have astigmatism. Recently developed online tests can screen for refractive errors, but they cannot replace the detailed in-office testing your doctor can provide.
The type of treatment you receive for astigmatism depends on the severity. Mild cases might reverse with eye exercises. Individuals with moderate to severe astigmatism require corrective lenses or surgery to help them see clearly.
How to Test for Astigmatism
Evaluation for astigmatism begins with your doctor taking a detailed patient history that includes any eye symptoms you are experiencing, the duration of the symptoms, and your overall health. Family history of astigmatism is also relevant.
The next part of diagnosis entails a series of tests:
- Visual acuity
- Keratometry (or the novel corneal topography)
Acuity testing measures the clarity of your vision. Your doctor will ask you to stand 20 feet away and read letters of varying sizes on a particular chart, the Snellen’s chart. The result of visual acuity testing is expressed as a fraction. For instance, you can have a visual acuity of 20/20, which is the value for someone with perfect vision.
However, people with astigmatism often complain of blurry vision, with visual acuity as low as 20/40. This implies that you must stand at 20 feet to read a letter that someone with perfect vision can read while standing 40 feet away.
Your doctor will shine light rays on your cornea measure their reflection using a keratometer. Keratometry determines the curvature of the front part of your eye. The procedure helps your doctor determine the lenses that can correct your refractive error.
An ophthalmologist or optometrist places different lenses in front of your eyes using a phoropter and uses a retinoscope to measure how each lens focuses light. Your doctor might ask you which lens gives you the clearest vision or use an instrument that measures the eyes’ focusing power automatically.
Refraction determines the degree of astigmatism and the lens power that best compensates for your eye curvature abnormalities to give you clear vision.
Advances In Testing
Technological advancement has seen the rise of a more accurate diagnostic test for astigmatism- corneal topography. This computerized test maps the contour of your cornea, outlining even the slightest curvature irregularity.
Corneal topography is superior to the traditional astigmatism diagnostic tests. Let’s take a closer look at the kinds of testing and their effectiveness.
At-Home or Online Test
Current online eye tests serve as essential screening tools for individuals who suspect they have astigmatism. While these tests are convenient, they do not replace the conventional in-office diagnostic exams. If your test results show likely astigmatism, you should follow up with an eye specialist.
An example of these online tests is the astigmatism mirror. Companies such as Opternative and Essilor offer various at-home astigmatism tests.
Results should be accurate if you carefully follow the steps and instructions for at-home astigmatism testing. But remember: these tests primarily serve as a screening tool. A follow-up comprehensive eye exam by a specialist is necessary.
Why Do You Need to be Diagnosed by a Doctor?
In-office eye testing is essential to diagnosing astigmatism because it is objective, unlike a self-assessment. It limits the likelihood of error and helps you obtain expert opinions.
Besides initiation of treatment for moderate to severe astigmatism, the doctor will advise how often you need to go for comprehensive eye examinations.
Since astigmatism often occurs with refractive errors, in-office diagnosis can help discover these disorders too.
What Happens After Testing and I Am Diagnosed?
If you are diagnosed with astigmatism, your doctor is likely to initiate a treatment based on the degree of abnormality. Mild astigmatism of around 0.75 diopters requires no treatment if you are asymptomatic.
If you have moderate or severe astigmatism, your doctor might prescribe corrective lenses (soft toric or rigid gas permeable lenses) to clear up your blurry vision. Laser surgery is the treatment of choice for those who want a long-lasting solution.
What if Tests Are Normal?
Astigmatism is just one of the causes of blurry vision and associated symptoms. If the astigmatism tests are normal, your doctor will run more tests to evaluate the other possible etiologies.
Optic neuritis, macular degeneration, glaucoma, and retinopathy also cause visual disturbances. Therefore, your doctor will perform tests such as slit lamp examination and tonometry to determine the cause of your eye symptoms.
How will you know if you have astigmatism?
Symptoms such as blurry vision, headache, and eyestrain can make you suspect a case of astigmatism. However, an in-office diagnosis consisting of a comprehensive eye exam is the most accurate way of determining whether you have astigmatism.
What are the symptoms of astigmatism?
Astigmatism mainly presents itself with blurry vision. But other symptoms such as headache, eye strain, squinting when trying to focus, and poor night vision can also occur in astigmatism.
How do I know if I need glasses for astigmatism?
Not everyone with astigmatism needs corrective lenses. If you have no symptoms, you might not need glasses. However, astigmatism can worsen over time, implying you might require glasses later even if you do not have any current symptoms. Generally, those with astigmatism over 1.5 diopters are the ones who need lenses. Presbyobypes with astigmatism of 1.0 will have a better vision if the curvature abnormality is corrected.
Eye Health Statistics. (2015) American Academy of Ophthalmology.
Comprehensive eye exams. American Optometric Association.
The doctor will ‘see’ you now: Online vs. in-person vision tests. (March 2018). CNN Health.
Astigmatism and vision: should all astigmatism always be corrected? (May 2013). British Journal of Ophthalmology.
Last Updated February 26, 2022
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