Eye & Vision Tests

Quick vision checks you can do at home with a screen: a calibrated eye chart for sharpness, two colour vision tests, an astigmatism clock dial and a blind spot test. They are screening tools that help you decide whether to book an eye examination, not a replacement for one.

Medical disclaimer: these tests are for information and screening only. They cannot diagnose any eye condition, check eye health or give a glasses prescription. See an optometrist or eye doctor for a full eye examination, and get urgent help for sudden changes in vision, eye pain, flashes or a shadow over your sight.

Which vision test should you take?

To check how sharp your eyesight is, use the eye test. It draws a tumbling E chart at the right size for your distance, after a one-minute calibration with a bank card, and gives your score per eye in the familiar 20/20 or 6/6 form. The astigmatism test is a clock dial: if the lines in one direction look darker with one eye, that points to astigmatism, a very common reason for blurred or doubled letters.

For colour, start with the red-green color blind test: twelve dot plates in the style of the Ishihara test, with two plates that separate the protan (red) and deutan (green) types. The color vision test works like the Farnsworth D-15: you put coloured caps in order around the colour circle, which also shows blue-yellow (tritan) problems and how strong a deficiency is. The blind spot test shows the natural blind spot every eye has, and measures where it sits.

How to get a fair result at home

  • Calibrate the screen where a test asks you to. A browser does not know the size of your screen, and letter sizes and angles depend on it.
  • Turn off colour filters: Night Light, Night Shift, True Tone, Eye Comfort, blue light glasses and dark-mode tints all change colours.
  • Measure the distance with a tape and keep browser zoom at 100%.
  • Test one eye at a time, covering the other with your palm without pressing. The better eye hides a weaker one when both are open.
  • Use good light and full screen brightness, and take the test when your eyes are not tired.

When to see an eye doctor

Book a full eye examination every two years, or every year for children, people over 60 and people with diabetes, even if online tests look fine: many eye diseases cause no symptoms until late. Book sooner if a test here shows a result worse than 20/40 in either eye, a clear difference between the eyes, signs of astigmatism or colour blindness you did not know about, or if your vision has changed. Seek urgent care the same day for sudden vision loss, a curtain or shadow over part of your sight, new floaters with flashes, double vision or a painful red eye.

Related pages

The screen itself matters for these tests. The screen size page measures your display with the same calibration, and the screen tests check for dead pixels and colour problems. For hearing, see the hearing frequency test.

Frequently asked questions

Are online eye tests accurate?
A calibrated chart at a measured distance gives a fair estimate of sharpness, and colour plates are a useful screen for colour blindness. But they only check a few things and depend on your screen, so they are screening tools, not a diagnosis.
Can an online test replace an eye exam?
No. An eye examination measures your prescription and checks the health of the eye, including pressure, retina and optic nerve, which no screen test can do.
How often should I have my eyes tested?
Every two years for most adults, and every year for children, people over 60, people with diabetes and anyone with a family history of glaucoma.
Can I test my child's eyes online?
The tumbling E chart works for children who can point in four directions, but children should have regular eye checks with a professional, because a lazy eye needs treatment early.
Do I need to calibrate for every test?
Only the tests that depend on size: the eye test, the blind spot test and the screen size page. The calibration is saved in your browser and shared between them.
Why do the colour tests need filters turned off?
Night modes and blue light filters tint the whole screen yellow or orange, which changes the colours the tests rely on and can make normal colour vision fail.

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