Colour blindness test. Cards being used to check for red-green colour blindness. The Ishihara test,which uses pseudoisochromatic plates,is the most widely used. Each card depicts a number formed from red dots on a background of green dots,or vice-versa. People suffering from red-green colour blindness cannot distinguish the numbers. Colour blindness is usually caused by an inherited genetic defect in the light-sensitive pigments of the eye,but it can be caused by optic injury or nerve diseases. Up to 8% of the male population is affected,and ten times more men have colour blindness than women. The number seen here is 29 | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / ANNABELLA BLUESKY |
Taille de l’image : | 4012 px × 4012 px |
Model Release : | Disponible |
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Restrictions : | - |