Standardized and calibrated light stimuli via head-mounted displays for investigating the non-visual effects of light

Light influences human physiology profoundly, affecting the circadian clock and suppressing the endogenous hormone melatonin. Experimental studies often employ either homogenous full-field stimulation, or overhead illumination, which are hard to standardize across studies and laboratories. Here, we present a novel technique to examine non-visual responses to light using virtual-reality (VR) head-mounted displays (HMDs) for delivering standardized and calibrated light stimuli to observers in a reproducible and controlled manner. We find that VR HMDs are well-suited for delivering standardized stimuli defined in luminance and across time, with excellent properties up to 10 Hz. We examine melatonin suppression to continuous luminance-defined light stimuli in a sample of healthy participants (n=32, mean{+/-}SD age: 27.2{+/-}5.6), and find robust melatonin suppression in 24 out of 32 participants (75% of the sample). Our findings demonstrate that VR HMDs are well-suited for studying the mechanisms underlying human non-visual photoreception in a reproducible and standardized fashion.