A comparative study of three tests for color vision.

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Abstract
A group of 200 men ranging in age from 17 to 56 was given 3 tests for color vision: (1) Pseudo-Isochromatic Plates by American Optical Co., (2) Tests for Color Blindness by Ishihara, and (3) Tests for Color Blindness by Milton B. Jensen. The pseudo-isochromatic test of 48 plates is similar to the Ishihara 13 plate test in that each plate has dotted numbers or letters on it in a different color or different shade of color from the dotted background. The test by Jensen has 4 plates all of which are made to look like faces of clocks. The subject is to report how many hands he sees and at what hrs. they point to. All 3 tests have at least one plate which the normal and color blind individual see alike. The other plates are supposed to differentiate between the normals and color blind in that they elicit entirely different verbal responses. The Pseudo-Isochromatic Plates were viewed at 3 ft. at eye level; the Ishihara at standing height above a display table; and the Jensen at 10 feet. Two points were counted off for each color blind response; nothing for normal response; and one point off for misreading, e.g., calling a "3" an "8", or a "7" a "2". The highest scores possible on each of the 3 tests as listed in order above were 86, 24, and 6 respectively. The results show the Pseudo-Isochromatic and the Ishihara in close agreement with each other (97.5%). An occasional normal or color blind individual diagnosed by one test will fall in the border-line category in the other. The short test by Jensen allows for no "border line" classification and is far less in agreement with either of the other tests as to what is a normal or color blind classification. If the commonly-used Ishihara test is accepted as normal, the Jensen test lacks adequate validity for diagnosis.

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