How the colourblind see the world

There are three main types of partial colour blindness: Red deficiency (protanopia), green deficiency (deuteranopia) and blue deficiency (tritanopia).

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The suffix -anopia refers to a complete absence of the cones that detect light, whereas -anomaly, as in deuteranomaly, tritanomaly and protanomaly, means the cones are present but mutated.

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Roughly one percent of men have protanopia, and another one percent have deuteranopia. Deuteranomaly is the most common, affecting six percent of men and 0.4 percent of women.

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Tritanopia affects less than one percent of men and women, and tritanomaly affects less than 0.01 percent of men and women.

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Most of the genes involved in colour blindness are on the X chromosome, which is why men are affected more than women.

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Monochromacy is complete colour blindness. People with this condition see the world in black and white.

Want to check your colour perception? The EnChroma website has an easy Ishihara test.

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