Project Summary/Abstract. The suppression of melatonin production by nighttime retinal light exposure has been linked to health risks to nightshift workers. Blue-blocking filters can preserve nighttime melatonin levels, and monocular light exposures can radically reduce nighttime melatonin suppression to as little as 10% of that observed for conventional binocular exposures. Our premise is that positioning a blue-blocking orange filter over one eye will preserve binocular vision while reducing light-induced melatonin suppression relative to a completely unfiltered viewing condition. This solution should not impede the performance of visual tasks that might require binocular vision, nor should it cause user discomfort. We propose a laboratory experiment (Aim 1) to determine whether blue- blocking filters and monocular viewing, alone or in combination, are effective for maintaining melatonin at night without affecting visual performance and subjective sleepiness (KSS). Aim 2 will be conducted at the Simulation Teaching and Research Center (STAR) at the Icahn School of Medicine at Mount Sinai to determine whether altered viewing interventions could influence melatonin levels and simulated task performance requiring depth perception (e.g., catheter / intra venous insertion in dummy) in healthcare workers. For Aim 3, involving nightshift working workers operating in actual hospital environments at Mount Sinai Hospital and Memorial Hospital in South Bend, IN, we will determine whether eyewear aimed at maintaining melatonin at night would be effective, practical, and socially acceptable. Aim 1 will employ a crossover within-subjects design, exposing subjects to 6 experimental conditions (monocular/binocular x filtered/non-filtered, 2 controls) over the course of 6 independent sessions. Aim 2 will employ a within-subjects design exposing subjects to 4 experimental conditions (control, filtered binocular, filtered monocular, unfiltered monocular/dominant eye occluded) over the course of 4 nightshifts (separated by at least a week). Aim 3 will be employ a within-subjects design similar to Aim 2 over the course of 4 one-week sessions (at least 3 shifts per session) with salivary melatonin levels, sleepiness scores, and Likert scale responses, as the output measures. This proposal is significant from a practical perspective because the methods to be tested could serve as elegant, inexpensive, personalized, non-invasive optical interventions to protect the natural synthesis of melatonin in night-shift workers. We will be addressing Healthy Work Design and Well-being (cross-sector). As part of the Research to Practice (r2p) activity, we will address need to maintain melatonin at night among nightshift nurses with a novel, but inexpensive technology, and evaluate its efficacy in practice.