Color Vision Test

What it measures

Whether you may have a red–green colour vision deficiency, the most common inherited type, which affects roughly 1 in 12 men and 1 in 200 women. It screens your ability to tell apart hues that lie along the red–green confusion axis.

How it works

You view a series of pseudo-isochromatic plates: a circle of coloured dots in which a number is hidden using dots whose hue differs from the background. Dot size and brightness vary randomly so only colour distinguishes the figure. You enter the number you see for each plate, and the count you read correctly indicates whether a red–green deficiency is likely.

Tips for an accurate result

• 1Turn off screen colour filters — Night mode, warmth and accessibility colour filters will all skew the result — disable them first.
• 2It screens red–green, not all types — Rare blue–yellow (tritan) deficiencies aren't reliably detected by red–green plates.
• 3Inherited deficiency is lifelong — If colour vision has always been this way, it's typically genetic and stable rather than a new disease.
• 4Sudden colour change needs a doctor — A new or one-sided loss of colour (especially with eye pain) should be assessed promptly.