Most people take the ability to see life in bright colours for granted. They make sure the colours of their clothing match, get hungry at the sight of a delicious red strawberry and enjoy all the colours of nature. But for some 180 million people around the world this colour experience remains partially or completely hidden – they either have red-green colour deficiency or blindness, have greatly reduced colour vision, or in very rare cases cannot distinguish any colours at all. This is colloquially known as colour blindness.
People with normal colour vision mix the three spectral colours red, green and blue to create all other colours. The cones, sensory cells on the retina, are responsible for this. They work only during the day: at night we actually see everything grey. However, not all colour blindness is all the same. Even though everyone thinks it's the same thing, the term covers many different defects. Experts distinguish the following conditions:
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