Types of colour blindness

Types of Colour Vision Deficiency

There are several types of colour vision deficiency, each caused by a different issue with the cone cells in the retina:

Deuteranopia / Deuteranomaly

The most common type (about 6% of men). Caused by missing or altered M-cones (medium wavelength). People with deuteranopia have difficulty distinguishing green from red and related hues.

Protanopia / Protanomaly

Affects about 2% of men. Caused by missing or altered L-cones (long wavelength). Red appears darker and can be confused with black, brown, or dark green.

Tritanopia / Tritanomaly

Very rare (less than 0.01% of population). Caused by missing or altered S-cones (short wavelength). Blue and yellow become difficult to distinguish.

Monochromacy

Complete colour blindness - seeing only in shades of grey. Extremely rare (affects about 1 in 30,000 people).