A new computer graphics test for red/green colour anomaly

Two new computer colour-monitor tests of colour vision have been devised and assessed on normal and anomalous subjects, as classified with a standard (Neitz) optical anomaloscope. In test 1, the relative luminance of the red and green phosphors was set to iso-luminance - where only colour and no luminance contrast is present - by alternating red and green at 25Hz and adjusting for minimum 'counter flicker'. This separates the eye's colour systems from its luminance system, as colour cannot follow this flicker frequency. In test 2 the minimum colour contrast, without luminance contrast, for discerning a figure was measured, with the minimally-distinct-border technique rather than 'counter flicker', for establishing the iso-luminance point. The figure used was one of six alternative letters, set slightly redder or greener than the red + green mixture background.

Using 13 normal and 24 anomalous subjects, test 1 was only able to distinguish the protanomalous subjects as a group; the normals and deuteranomalous subjects had overlapping scores. Test 2 succeeded in distinguishing the normals from the anomalous subjects, ad it also separated the anomalous subjects successfully into protanomalous and deuteranomalous, corresponding to the Neitz anomaloscope distinctions.

The computer tests, being automated, can be carried out by unskilled testers; but there are limitations and some dangers of artefacts. Although probably not worthwhile for colour testing alone, the system can be extended to present and analyse many other visual - including high level cognitive - tests, and so seems worth developing.