Can you see the number?
Plates in the style of the Ishihara test help screen for red-green and blue-yellow colour vision deficiency. Find the hidden number in each plate.
For screening only. It does not replace an eye examination. If your vision changes, see an ophthalmologist (eye doctor).
What number do you see in the plate?
Understanding colour vision
Colour vision deficiency affects about 8% of men and 0.5% of women worldwide.
Red-green deficiency
Protanopia and deuteranopia
The most common type. People find it hard to tell reds from greens. It is often inherited on the X chromosome and affects about 8% of males.
Subtypes: protanomaly (reduced red) and deuteranomaly (reduced green, the most common of all).
Blue-yellow deficiency
Tritanopia and tritanomaly
Less common. People find it hard to tell blues from yellows. It affects men and women equally, about 1 in 10,000 people.
Can be acquired: it sometimes develops with age, optic nerve disease or certain medicines.
Complete colour blindness
Achromatopsia
Seeing only in shades of grey is extremely rare (1 in 30,000). It usually comes with light sensitivity and reduced sharpness of vision.
Note: most "colour blind" people do see colour, just a reduced or shifted range.