Colour vision classification – comparing CAD and CIE 143:2001 International recommendations for colour vision requirements in transport

Abstract

Purpose: To evaluate the colour vision severity classification standard ‘CIE 143:2001 International recommendations for colour vision requirements in transport’ (CIE 143:2001), which has become out of date because of the lack of commercial availability of required colour vision tests. Methods: One-hundred-five subjects had colour vision tested and colour vision severity classified according to a modified CIE 143:2001 algorithm that included pseudoisochromatic plates (Ishihara's test and Hardy Rand Rittler (HRR) 4th edition), Optec 900 lantern and Farnsworth D-15. Subject's results and colour vision severity classification were compared to performance and colour vision severity classification on the computerized ‘Colour Assessment and Diagnosis’ (CAD) test. Results: According to CIE 143:2001, using Ishihara’s test, Optec lantern and Farnsworth D 15, 11 subjects (10%) were category I (normal), 16 (15%) were category II (mild), 48 (46%) were category III (poor), and 30 (29%) were category IV (severe). Classified by CAD score, 10 (10%) were category I, 11 (10%) were category II, 41 (39%) were category III, and 43 (41%) were category IV. The correlation between the two estimates of the severity of colour vision loss (i.e. CIE 143:2001 and CAD) was high, with a Kendall’s Tau test of 0.81 (τ = 0.81 p < 0.001). A suggested CIE 143:2001 classification including new CAD score limits improves the classification correlation to 0.90 (τ = 0.90 p < 0.001) for all diagnoses. Conclusion: The colour vision severity classification standard ‘CIE 143:2001 International recommendations for colour vision requirements in transport’, has not implemented new diagnostic tools with better accuracy. We propose three possible revisions to the CIE 143:2001 algorithm, based on the availability of CAD: (1) Replacing the current CIE 143:2001 algorithm using new CAD threshold limits, (2) Use of CAD as a secondary test to Ishihara's test and HRR or (3) Revising the current CIE 143:2001 algorithm using Ishihara's test, HRR, Optec 900 and FD15.