Color vision assessment‐1: Visual signals that affect the results of the Farnsworth D‐15 test

Abstract

The Farnsworth D-15 test (D-15) is commonly used to screen for moderate to severe congenital color vision deficiency. The aim of this study was to establish reliable D-15 statistics for normal, deutan and protan subjects, and to investigate the different visual signals one can use to carry out the test, even in dichromats and rod monochromats. Six hundred and seventy-four subjects were examined using the D-15, the Colour Assessment and Diagnosis test and the Nagel anomaloscope. A rod monochromat and five dichromats were tested using the standard D-15 protocol before the caps were separated into two groups and subjects were asked to repeat the task. D-15 spectral radiance data, measured under D65 illumination, were used to estimate differences in photoreceptor excitations for each of the caps. When no crossings and up to two adjacent transpositions on the D-15 results diagram are accepted as a pass, 100% of normal trichromats, 54% of deutans and 43% of protans pass the D-15. A rod monochromat and two protanopes and deuteranopes were able to complete the D-15 when the caps were separated into two groups, despite severe loss or even complete absence of color vision. When up to two adjacent transpositions are accepted 50% of color deficient subjects, some with severe red/green loss, pass the D-15. While the D-15 is normally used to screen for moderate to severe color deficiency, subjects with severe loss can still use combined, residual red/green, yellow/blue and luminance signals to pass.

Color vision assessment‐2: Color assessment outcomes using single and multi‐test protocols

“…tests. 40 Since subjects with more severe RG loss tend to fail more IH plates, the number of errors the subject makes on the IH test has been incorrectly assumed to be a good measure of the severity of RG color vision loss. In practice, the number of errors subjects make correlate very poorly with severity of loss.…”

“…54 The D-15 and CU tests, when used in isolation, fail to achieve either of these objectives. 40,55 Table 3 lists the outcome of the three multi-test protocols investigated in this study. Protocol A was designed for use in aviation and other transport related occupations.…”

“…39 The number of major crossings and adjacent transpositions were recorded and the classification of the D-15 (the number of "protan/deutan/ tritan" crossings) was determined using the method described in the first article in this series. 40 The subject's task on the CU test is to select which of the four peripheral colors is perceived to be least different to the central color. Three peripheral colors represent typical isochromatic confusions with the central color, for each type of defect.…”

“…28,46 The test has been fully described in earlier publications. 2,40 The RG and YB CAD thresholds are approximately linearly proportional to the cone contrasts generated by the colored stimulus. 47 This observation justifies why the measured thresholds are appropriate to quantify severity of color vision loss.…”

Quantitative scoring methods of the Farnsworth D15 and Waggoner computerized D15 color vision tests in clinical practice

“…This is because the test agrees with the ability of color vision defectives' individuals to discriminate colors in different occupational jobs 21‐24 . Furthermore, the FR‐D15 has less than moderate agreement with the computerized color vision tests, where most of the color defectives in the mild category would pass the FR‐D15 and fail the computerized tests 18,25 . This raised concerns about using the FR‐D15 test as a screener test in terms of the pass/fail basis.…”