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Heart rate (HR) and heart rate variability (HRV) indices during blue light exposure from different incidence angles on the eye (blue bars) and subsequent dark periods (gray bars). Values are least square means and standard errors of the means adjusted for the effects of exposure order. HF high frequency, LF low frequency, LF/HF LF-to-HF power ratio, SDNN standard deviation of normal-to-normal R–R intervals
