Ishihara’s Test for Color Deficiency by Dr. Shinobu Ishihara (English)

Light color square will be bright on dark background and dark color will be bright on light background. This is due to the background as a factor in color perception. The test to establish this phenomenon consists of two color backgrounds i.e grey and red with five small round color bits ( blue, yellow, green, violet and orange)

Rods and cones are the specialized nerve cells of retina, which is photosensitive. It is due to the cones we respond to colors whereas rods help in night vision. The color zones of retina are smaller than the visual field. The middle part of the retina is sensitive for blue and yellow. The central part is sensitive for all the colors except grey and brightness. However peripheral zones are highly sensitive to brightness. It is true to the fact that everyone is completely color blind in the periphery of retina. It is highly significant to note that the patch of any color looks as grey when seen in the marginal visual field. To measure the retinal color zones perimeter is used. This measurement is called mapping of retinal color zones.