Colour blindness test. Plate 4 of an Ishihara test. Invented by Japanese physician Dr Shinobu Ishihara in 1917,the charts use arrangements of coloured dots to test for red-green colour blindness. In this plate those with normal vision will see 29,those with red-green deficiencies will see 70. The full test comprises 38 plates that test the type and severity of deficient colour vision. Colour blindness is usually caused by an inherited genetic defect in the light-sensitive cells (cones) of the eye. Colour blindness can also be caused by optic injury or nerve diseases | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library |
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