Colour vision deficiency and colour blindness

When colours look different

Do you find it hard to tell some colours apart, for example red from green? It could be a colour vision deficiency (dyschromatopsia), an alteration in colour perception, often also called colour blindness.

Colour blindness and colour vision deficiency: what they are

Colour vision deficiency is a reduced ability to distinguish certain shades. The most common form affects the distinction between red and green, and this is what the term colour blindness usually refers to. Much rarer are the forms affecting blue and yellow, and achromatopsia, in which only shades of grey are seen.

In most cases it is inherited and mainly affects men: in Europe it affects about 8 men in 100 and fewer than 1 woman in 100.

How to recognise it

Since it is present from birth, it often goes unnoticed for years: people who have it do not know they see colours differently. A simple colour vision test, using special plates, can detect it. It is useful to do it in children too, before they start school.

If the change in colour perception appears suddenly or gets worse over time, it is not inherited: in this case, see an ophthalmologist.

Can it be corrected?

Inherited colour vision deficiency cannot be cured, but there are lenses with specific filters that, in some people, increase the contrast between certain colours and make them easier to tell apart. They do not restore normal colour vision, and results vary from person to person.