Abstract

The description and measurement of defective color vision has been a problem of long standing for clinicians. Since subtle color defects are known to be correlated with some systemic disorders and toxic conditions, thresholds of discrimination for each color would be most informative, but neither they nor any closely related measurements are obtained by the conventional color tests. Louise Sloan in 1943 devised a Color Threshold Tester¹ which was used briefly by the Air Force, but it was not widely accepted because of the cumbersome procedure involved and the lack of an effective data system. The so-called "New Color Test" of P. Lanthony² undertook to determine thresholds of discrimination, which were plotted on the uniform chromaticity circle of Munsell to reveal a neutral zone or area. Unfortunately the test requires arrangement and scoring of 70 colored and gray caps or buttons, so it is nearly as tedious as the Farnsworth-Munsell 100-Hue test³. Sahlgren's Saturation Test⁴ is another attempt at determining thresholds, but it is limited to the blue and blue-purple part of color-space. Grützner⁵ demonstrated neutral bands in the visible spectrum of patients with acquired color vision defects, but his system was not easily adapted to clinical use. Marré⁶ used a modification of Wright's Trichromatic Colorimeter⁷ to measure the first saturation step from white throughout the whole spectrum, which is exactly what we would all like to do, but with a less complicated and time-consuming method. Herewith we are presenting Marré's type of data, which we obtained and plotted on a color circle with the chromagraph⁸. We believe that this circle concept is more acceptable to clinicians than either the conventional spectral sensitivity curves or the C.I.E. chromaticity diagram. The circle developed by the chromagraph has been confirmed mathematically and the colors calibrated by the Bureau of Standards, so threshold points on it can be transformed into C.I.E. coordinates if necessary. The system applies equally well to congenital and acquired color defects, but the distinction can usually be made without difficulty.

© 1985 Optical Society of America