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Visual comfort assessed with the headache and eye strain scale (1–4 (severe)) during a simulated night shift in long-wavelength narrow-bandwidth light (triangles) and short-wavelength narrow-bandwidth light (circles). Data points are the estimated marginal means with error bars indicating standard error. Significant differences between light conditions indicated for variables with a significant Light by Time interaction only. * = p < 0.05, ** = p < 0.01, *** = p < 0.001.
