Colour Vision Deficiency

Post date: 
Wednesday, 15 November 2017
Ishihara test image [Credit: Science Museum, London. Wellcome Images]

With the help of photos that replicate different types of colour vision deficiencies, NB Online finds out what colour blindness "looks" like, and what it’s like to live with the condition.

People who have colour vision deficiency (colour blindness) find it difficult to identify and distinguish between certain colours. 

In most cases colour blindness is inherited, though it can be developed in later life if an injury is incurred.

Worldwide, about eight per cent of men (1 in 12) and 0.5 per cent of women (1 in 200) have some form of colour vision deficiency (CVD) and about half of these have a moderate or severe condition. Those with an especially mild condition may not even be aware that they have it.  

How does it work?

Our perception of colour begins with light entering the eye and stimulating one of three cones (receptor cells within the eye). Each cone is sensitive to different wavelengths and pass on a signal to be processed in the brain.

When all three cones are working properly, we have "normal vision". However, differences in how sensitive these cones are to light, or for people who have fewer than three cones, results in a range of different colour vision deficiencies.

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