New approach to establish safe colour vision limits for occupational environments

Abstract

Purpose Concern has been expressed that current colour vision (CV) standards in occupational environments tend to screen for normal trichromacy and may not therefore relate directly to actual CV requirements within specific working environments. Methods The new approach of establishing CV limits for specific occupations involves: ‐ measuring chromatic sensitivity and investigating the variability amongst normal trichromats ‐ accurate assessment of the severity of CV loss ‐ identifying the most important colour‐critical tasks at the work place when no redundancy is involved and discrimination of colour differences is most difficult ‐ simulating the most critical colour‐based tasks identified ‐ correlating the level of chromatic sensitivity and the subject’s performance of these tasks. Results A large number of normal trichromats and colour deficient observers have been examined on the CAD (Colour Assessment & Diagnosis) test. The test provides an accurate measure of the severity of CV loss (for red‐green and yellow‐blue discrimination) and diagnoses the class of deficiency involved. The findings from this study so far have produced minimum CV requirements in two specific occupational environments. These limits specify the level of chromatic sensitivity loss below which colour deficient subjects no longer perform the most demanding colour related tasks with the same accuracy as normal trichromats. Conclusion The new approach provides evidence‐based guidelines for minimum CV standards that can be implemented through objective testing without having to rely on either arbitrary limits or normal trichromacy. Further, this approach can be extended to other occupational environments where colour is important for carrying out visual tasks.