Astigmatism Test Online: Quick Clock Dial Check
Do some lines look darker or blurry? Try this clock dial test, learn what it means and when to see an eye doctor.
This is a screening tool, not a medical diagnosis. Results depend on your screen, brightness and lighting. See an eye doctor for a proper exam. Medical disclaimer
Last updated: . Based on the sources listed below.
Clock dial check
- Wear your usual glasses or contact lenses, and keep your head straight.
- Cover one eye. Sit about an arm’s length from the screen, with the page at its normal size and the screen at normal brightness.
- Look at the center of the dial. Do all lines look equally dark and sharp, or do some look darker, sharper or blurrier?
- Now test the other eye.
What do the results mean?
| What you see | What it may mean | What to do |
|---|---|---|
| All lines look equally dark and sharp | No hint of astigmatism in this check. Mild astigmatism might not show. | Keep up regular eye exams. |
| Some lines look darker or sharper than others | Can be a sign of astigmatism, but a screen, a smudge or tired eyes can cause it too. | Book an eye exam. |
| All lines look blurry | Could be another focusing problem, or the wrong glasses. | Book an eye exam. |
This is our plain-words reading of the test. It is not a diagnosis. In a clinic, the dial is used while a professional controls the lenses (StatPearls).
What is astigmatism?
Astigmatism is an imperfection in the normal curvature of the eye’s cornea or lens (AAO: What Is Astigmatism?). Because of that shape, near and far vision can both be blurry. It can come with nearsightedness or farsightedness. Most people have between 0.5 and 0.75 diopters of astigmatism, and people with 1.5 or more typically need contacts or glasses to see clearly (AAO: What Is Astigmatism?).
How is astigmatism diagnosed?
An eye doctor can check for astigmatism as part of an eye exam, which is simple and painless (NEI: Astigmatism). Testing may include reading an eye chart, looking through a phoropter, an autorefractor and a keratometer that measures the curve of the cornea (AAO: What Is Astigmatism?). Try our online eye test or the printable eye chart to see how sharp letters look to you, and read the medical disclaimer.
When should I see an eye doctor?
If you often have blurry vision, squint, get headaches or eye strain, or have trouble seeing at night, book an eye exam. This is especially important for children, who may be less likely to realize that their vision is not normal (NEI: Astigmatism).
Frequently asked questions
What does the astigmatism clock dial test show?
It shows whether some radiating lines look darker or sharper than others. Eye care professionals use a clock dial and ask which lines look darkest or clearest, according to StatPearls. On a screen it is only a hint. The National Eye Institute says the only way to find out is an eye exam.
What are the symptoms of astigmatism?
The National Eye Institute lists blurry vision, needing to squint to see clearly, headaches, eye strain and trouble seeing at night. Mild astigmatism may cause no symptoms. The American Academy of Ophthalmology adds that these symptoms do not always mean astigmatism, so an exam is needed.
What causes astigmatism?
It happens when the cornea or lens has a different shape than normal, so light bends differently as it enters the eye. The American Academy of Ophthalmology says the risk is inherited and that it can also follow eye disease, injury or surgery. Reading in low light does not cause it.
How is astigmatism treated?
The most common treatments are eyeglasses or contact lenses, and some people can have surgery that reshapes the cornea. The National Eye Institute says that if your astigmatism is mild, you may not need treatment. Your eye doctor can tell you what is best for you.
Can children have astigmatism?
Yes. The American Academy of Ophthalmology says astigmatism is common in children and may cause blurry vision, squinting, headaches or trouble seeing the board at school, though children may not complain. Without treatment it can affect school and sports performance, so routine eye exams matter.
Sources
- National Eye Institute (NIH). Astigmatism. Last updated December 4, 2024. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/astigmatism
- American Academy of Ophthalmology. What Is Astigmatism? https://www.aao.org/eye-health/diseases/what-is-astigmatism
- StatPearls. Subjective Refraction Technique: Astigmatic Dial. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK589695/
All sources were read on October 11, 2026. We only state what the sources say, and we do not invent numbers. These pages have not been reviewed by an eye care professional. Spot a mistake? Email info@colorblindcheck.app.