Ishihara colour charts are ideal for the screening of hereditary red-green colour vision defects. Available in four different versions, book format.
he test consists of a number of colored plates, called Ishihara plates, each of which contains a circle of dots appearing randomized in color and size. Within the pattern are dots which form a number or shape clearly visible to those with normal color vision, and invisible, or difficult to see, to those with a red-green color vision defect. Other plates are intentionally designed to reveal numbers only to those with a red/green color vision deficiency, and be invisible to those with normal red/green color vision. The full test consists of 34 plates, but the existence of a severe deficiency is usually apparent after only a few plates. There are also Ishihara tests consisting of 14, 24 or 34 test plates.