Using the Invisibility of Metamers to Create a New Anomaloscope Color Blindness Test

The goal of this work is to develop a portable and accurate colorblind test that has advantages over the HRR and Ishihara plate tests, including that it is easier and faster to perform, does not require the subject to identify alphanumeric characters or geometric shapes, provides unambiguous results to the provider without interpretation, and is at least 8 times faster. The advantage over prior anomaloscopes is that it can be made in a hand-held version, uses binary matching choices rather than having the subject match colors with a tuning knob, and uses optimal reference color choices determined from established knowledge of human color perception. To successfully achieve this, cone spectral sensitivity curves and all subsets of four LEDs from a set of eight spanning the visible spectrum, the 1x4 metamer solution for a reference color for normal vision, deuteranomaly, and protanomaly are calculated. From these solutions, the optimized set of 4 LEDS was determined by maximizing the average angle between the normal, deuteranomaly, and protanomaly metamer solution vectors in the XYZ color space. To perform the test, the subject is asked to determine the best match for color and brightness in side-by-side display panels illuminated with distinctly different reference metamer color pairs for normal, deuteranomaly, and protanomaly vision. This allows the operator to directly and unambiguously determine the subject’s color vision type. The average duration to perform the tests are 30, 253, and 281 seconds for the anomaloscope, Ishihara 38 plate test, and HRR 24 plate test, respectively. When determining whether the subject has normal vision or is colorblind, the anomaloscope and HRR test results agreed for all 102 subjects. Because this rendition of the anomaloscope was designed to only distinguish between normal, deuteranomalous, and protanomalous vision, the 7 subjects that the HRR determined to be tritanomalous were not included in the results presented hereafter. The HRR 24 plate test and the anomaloscope agreed in their diagnosis 91/95 = 96% of the time, the Ishihara 38 plate test and the anomaloscope agreed in their diagnosis 94/101 = 93% of the time, and the HRR and the Ishihara agreed in their diagnosis 89/95 = 94% of the time. The approach described here can be extended to other types of color blindness.