Use of the MacAdam Ellipses for Psychophysical Evaluation of Color Discrimination in Chronic Heavy Smokers

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Cigarette smoke is a complex chemical mixture that has health-damaging components, such as carbon monoxide, ammonia, pyridine, toluene, and nicotine. Cognitive functions have been well documented in heavy smokers, but visual perception has been less characterized. The purpose of the present study was to assess the influence of chronic heavy smoking on color discrimination. We evaluated color discrimination in healthy heavy smokers (n = 16), deprived smokers (n = 16), and healthy nonsmokers (n = 16). The participants were 20–45 years old and were evaluated using a psychophysical forced-choice method. In this method, the volunteers had to choose the pseudoisochromatic stimulus that contained a test frequency at 4 directions (e.g., up, down, right, and left) in the MacAdam ellipses test, which is commercially available as the Cambridge Colour Test. All of the groups were matched for gender and level of education. All of the participants were free of any neurological disorder, cardiovascular disease, and identifiable ocular disease, and they had normal or corrected-to-normal visual acuity. No abnormalities were detected on the fundoscopic examination or optical coherence tomography examination. Smokers had lower color discrimination compared with nonsmokers (p < .015). Deprived smokers presented lower discrimination than smokers and nonsmokers. The largest differences were observed for medium and long wavelengths. These results suggest that cigarette smoking, chronic exposure to its compounds, and withdrawal from nicotine affect color discrimination. This highlights the importance of understanding the diverse effects of nicotine on attentional bias.

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