Aviation-relevent epidemiology of color vision deficiency

Abstract

Introduction: The Colour Vision Study Group of Transport Canada undertook a prevalence review to ascertain the degree and type of color vision deficiency (CVD) common in different populations. This was performed as a first step toward establishing whether a bone fide occupational requirement for color vision in aviation can be determined.

Literature search: Peer-reviewed articles with large populations and appropriate methodology for measuring CVD were assessed. Those pertaining to congenital CVD were cross-sectional prevalence studies with greater than 100 subjects assessed with a combination of pseudoisochromatic plates (PIPs) and Farnsworth D15 and/or an anomaloscope. Of 162 papers reviewed, 36 met these criteria for inclusion in the congenital CVD section. Acquired CVD papers were included based on the quality of color vision tests employed. CONGENITAL CVD: Data on congenital and acquired CVD are presented separately in parts 1 and 2. Part 1 demonstrates that although the prevalence numbers for North American and European populations are consistent with those reported in reference texts, congenital CVD is actually less prevalent in Asian, African, and Native populations. Therefore, the reported overall 8% prevalence of CVD in men applies only to Euro-Caucasians and is significantly lower in other racial groups. Possible evolutionary implications of dichromatism in humans are explored. ACQUIRED CVD: In this section the current understanding of acquired color vision deficiency, with an estimated prevalence ranging from 5 to 15% (51,95), is reviewed. Acquired CVD is frequently associated with significant impairment of visual acuity and/or visual field. However, many ocular diseases and drugs do primarily affect color vision, independent of other visual function, and one must remain vigilant to their presence.

Conclusion: Congenital CVD is present in a consequential percentage of men, but considerable variability exists in different populations (2-8%). Acquired CVD may elude detection, but if severe is also associated with loss of visual acuity and/or visual field. Senescence remains the most common and increasingly prevalent cause for acquired CVD.