Impairment of color vision in aircraft maintenance workers

Purpose The purpose of the study was to examine possible persisting effects to color vision in a group from the Royal Australian Air Force who had exposure to formulations containing neurotoxins during F-111 fuel tank maintenance, relative to two contemporaneous comparison groups. Methods Color vision was tested in 512 exposed personnel, 458 technical-trade comparisons, and 330 non-technical comparisons using the Ishihara test plates and the Lanthony D-15 Desaturated Color disk arrangement test. Participants were excluded if they failed the Ishihara test as this indicates congenital color blindness. From the Lanthony results, the type of color deficient vision (CDV) was diagnosed, and additionally, the Bowman's color confusion index (CCI) was calculated. Regression models were used to examine whether there was an association between color vision deficiencies and F-111 fuel tank maintenance, adjusting for possible confounders. Results The CCI ranged from 1 to 2.8 (median 1.2, quartiles 1.1, 1.4) in the 2,600 eyes tested. Forty five percent of all participants had blue-yellow CDV in at least one eye. Deficiencies of this nature are caused by environmental exposures. Logistic regression demonstrated statistically significant differences in CCI category in the exposed group versus technical group (odds ratio 1.7: 95% CI 1.3-2.0) and a blue-yellow confusion in the exposed group versus technical group (odds ratio 1.4: 95% CI 1.1-1.7). No differences were observed between the exposed group and the non-technical group. Conclusion The results indicate reduced color discrimination among the exposed subjects compared to one of two control groups. The findings may be due to previous exposure to solvents among the air force personnel.