Colour vision requirements in visually demanding occupations

Abstract

Normal trichromatic colour vision (CV) is often required as a condition for employment in visually demanding occupations. If accurate CV tests were available Q2 to enforce this requirement, a significant percentage of subjects with anomalous, congenital trichromacy who can perform the suprathreshold, colour-related tasks encountered in many occupations with the same accuracy as normal trichromats would fail. These applicants would therefore be discriminated against unfairly. One solution to this problem is to produce minimum, justifiable CV requirements that are specific to each occupation. This has been done successfully for commercial aviation (i.e. the flight crew) and for Transport for London train drivers. An alternative approach is to make use of new findings and the statistical outcomes of past practices to produce graded, justifiable CV categories that can be enforced. To achieve this aim, we analysed colour assessment outcomes and quantified severity of CV loss in 1363 subjects. The severity of CV loss was measured in each subject and statistical, pass/fail outcomes established for each of the most commonly used, conventional colour assessment tests and protocols. This evidence and new findings that relate severity of loss to the effective use of colour signals in a number of tasks provide the basis for a new colour grading system based on six categories. A single colour assessment test is needed to establish the applicant's CV category which can range from 'supernormal', for the most stringent, colour-demanding tasks, to 'severe colour deficiency', when red/ green CV is either absent or extremely weak.

Detection of Early Loss of Color Vision in Age-Related Macular Degeneration – With Emphasis on Drusen and Reticular Pseudodrusen

“…These limits are based largely on studies of minimum color vision requirements carried out within visually demanding occupations. 13 The maximum possible YB CAD thresholds correspond tõ 18 CAD units as opposed to maximum RG thresholds of 34 CAD units. The lower upper limit that can be achieved for YB thresholds is caused by the much larger YB color signals needed at threshold and the limits imposed by the visual display, which allows higher saturation for RG than YB.…”

“…11 Under optimum conditions, young, normal trichromats require only 0.4% L-and 0.8% M-cone contrast changes to detect RG color differences (at threshold), but 7% S-cone contrast changes are needed to reach threshold in the case of YB color differences. 12,13 The high sensitivity for detection of RG or YB color signals and the large number of stages involved in chromatic processing makes color assessment particularly suitable for detecting changes caused by retinal disease. A systematic review of 15 studies reveals loss of chromatic sensitivity in diseases of the retina with a tendency toward greater YB loss.…”

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

“…The CAD test has demonstrated close to 100% sensitivity and specificity in detecting CVD and in classifying the type of deficiency involved (Marechal & al. 2018;Barbur & Rodriguez-Carmona 2017). The severity of both RG and YB colour vision loss is quantified in CAD units as Standard Normals (SN) 1 .…”

Case for a new corticosteroid treatment trial in optic neuritis: review of updated evidence

“…Validated, quantitative tests are now available to test low-contrast visual acuity (LCVA), including the Mars contrast sensitivity chart, and colour vision 15 16. A seven-point change on a 2.5% LCVA Sloane letter chart is considered as clinically meaningful 15.…”

“…A seven-point change on a 2.5% LCVA Sloane letter chart is considered as clinically meaningful 15. Highly accurate quantification of acquired dyschromatopsia is possible using the CAD test, which has therefore become standard in the aviation industry 16. The quality of calibration of the CAD and validated age-related normative data to judge on clinical meaningfulness makes it a good choice for a multicentre trial setting 6.…”