The colours of the symbols lie on the protan, deutan or tritan achromatic confusion loci and become increasingly saturated as the patient proceeds through the plates. These are followed by 14 plates designed to grade the severity of the deficiency and to differentiate protans, deutans (10 plates) and tritans (four plates).

Its classification of protans and deutans is useful but the Medmont C‐100 test is better. Conclusions: The test is as good as the Ishihara test for detection of the red‐green colour vision deficiencies but unlike the Ishihara, also has plates for the detection of the tritan defects. Not all dichromats were classified as ‘strong’, which was one of the goals of the re‐engineering and those graded as ‘medium’ and ‘strong’ included dichromats and those who have a mild colour vision deficiency based on the results of the Farnsworth D15 test and the anomaloscope range. All those graded as having a ‘mild’ defect by the Richmond HRR test passed the Farnsworth D15 test and had an anomaloscope range of 30 or less.

Those with red‐green colour vision deficiency were correctly classified as protan or deutan on 86 per cent of occasions, with 11 per cent unclassified and three per cent incorrectly classified. Sensitivity and specificity become 0.98 and 1.0, respectively, when the fail criterion is three or more errors.

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