A Critical Evaluation of Pseudo-isochromatic Plates and Suggeestions for Testing Color Vision *

The importance of including an adequate test for the discovery of deficiencies in color vision in any thorough medical examination of students has long been recognized; it is obviously desirable to detect at an early age those individuals who will be excluded from pursuing careers in occupations which require good color perception. For several years the Ishihara color vision test was used as part of the annual medical examination of the students at an eastern preparatory school, but in the 1941 examinations the pseudo-isochromatic plates published by the American Optical Company and engraved, printed, and copyrighted by the Beck Engraving Company in 1940 were used. In the course of testing the color vision of 726 male adolescents with these plates, we noted that only a small percentage of individuals gave the correct response to every plate, that a large number failed more than ten per cent of the plates, and that a variety of different responses were made to the same plate by apparently normal individuals. Our results from that testing program yielded so many individuals about whose color vision we were in doubt that we decided to make a critical evaluation of these color vision test plates and to attempt to devise methods of using those plates which would produce more uniform and less confusing results.