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

Abstract 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. Competing Interest Statement M.S. declares the following potential conflicts of interest in the past five years (2021-2025). Academic roles: Member of the Board of Directors, Society of Light, Rhythms, and Circadian Health (SLRCH); Chair of Joint Technical Committee 20 (JTC20) of the International Commission on Illumination (CIE); Member of the Daylight Academy; Chair of Research Data Alliance Working Group Optical Radiation and Visual Experience Data. Remunerated roles: Speaker of the Steering Committee of the Daylight Academy; Ad-hoc reviewer for the Health and Digital Executive Agency of the European Commission; Ad-hoc reviewer for the Swedish Research Council; Associate Editor for LEUKOS, journal of the Illuminating Engineering Society; Examiner, University of Manchester; Examiner, Flinders University; Examiner, University of Southern Norway. Funding: Received research funding and support from the Max Planck Society, Max Planck Foundation, Max Planck Innovation, Technical University of Munich, Wellcome Trust, National Research Foundation Singapore, European Partnership on Metrology, VELUX Foundation, Bayerisch-Tschechische Hochschulagentur (BTHA), BayFrance (Bayerisch-Französisches Hochschulzentrum), BayFOR (Bayerische Forschungsallianz), and Reality Labs Research. Honoraria for talks: Received honoraria from the ISGlobal, Research Foundation of the City University of New York and the Stadt Ebersberg, Museum Wald und Umwelt. Travel reimbursements: Daimler und Benz Stiftung. Patents: Named on European Patent Application EP23159999.4A ("System and method for corneal-plane physiologically-relevant light logging with an application to personalized light interventions related to health and well-being"). With the exception of the funding source supporting this work, M.S. declares no influence of the disclosed roles or relationships on the work presented herein. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. Footnotes Revisions throughout the manuscript reflecting peer-review comments.