255 Spectrophotometric Properties of Commercial Blue-Blocking Lenses in Sunlight

Introduction Blue-blocking glasses are increasingly used as an intervention for jet-lag and other situations where an individual wishes to promote a “dark” signal despite the presence of ambient light. However, most studies on blue-blockers are done under controlled laboratory settings using emissions generated from electric light sources. The present study evaluated the performance of commercially available blue-blockers under daytime sunlight conditions. Methods A calibrated spectroradiometer (Ocean Insight), cosine corrector, optic fiber, and software package were used to measure the absolute irradiance (uW/cm^2/nm) available midday in a standardized location that received direct sunlight. Thirty-one commercially available blue-blockers were individually placed in front of the cosine corrector and intensity was measured and analyzed. Each lens was tested for its ability to block visible light, as well as light within the 440-530nm range. Lenses were evaluated individually and grouped by lens type: red-tinted lenses (RTL), orange-tinted lenses (ORL), orange-tinted lenses with blue reflectivity (OBL), brown-tinted lenses (BTL), yellow-tinted lenses (YTL), and clear lenses with blue reflectivity (RBL). Results Across the full spectrum, RTL blocked 66% of the light, OTL blocked 60%, OBL blocked 43%, BTL blocked 56%, YTL blocked 28%, and RBL blocked 20%. When the range was restricted to 440-530nm, RTL blocked 99%, OTL blocked 96%, OBL blocked 90%, BTL blocked 66%, YTL blocked 38%, and RBL blocked 17% of the light. Variation across lens types was significant for the full spectrum (one-way ANOVA, p < 0.0001) as well as the 440-530nm range (one-way ANOVA, p < 0.0001). Individual lenses showed variability in performance, though this variability was smaller than the between-group differences. Conclusion Under daylight conditions, red and orange lenses (RTL, OTL, and OBL) blocked at least 90% of the light in the 440-530nm range. Notably, RBL lenses restricted the most short-wavelength light as a proportion of the total light blocked. These data suggest that RTL, OTL, and OBL are effective at blocking the most circadian photosensitive components of daylight at the cost of reducing total illumination. Support (if any) R01MD011600, R01DA051321