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143:2001 International recommendations for colour vision requirements in transport’ (CIE 143:2001), which has become out of date because of the lack of commercial availability of required colour vision tests.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.