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Elise Noel Harb, Michelle Chan, Amanda Tran, Christine Frances Wildsoet; Characteristics of Indoor and Outdoor Light Exposure Differ With Refractive Status in Young Adults. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2473.
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© 2017 Association for Research in Vision and Ophthalmology.
Reports of apparent protective effects against myopia of outdoor exposure has led to speculation about the influences on refractive development of light intensity and spectral composition, both of which have shown to significantly affect eye growth in animal models.
UC Berkeley students (n=2 non-myopes, SER range: +1.63 to 0 D; n=3 myopes, -2.25 to -6.25 D), participated in this preliminary study. Subject data was collected during the “non-academic” year from light sensor wristwatch devices (Actiwatch Spectrum Pro, 400-700 nm) worn on their non-dominant arm over clothes for 7 days, with exposure collected at 1-min epochs. Light intensity consistent with outdoors (≥1000 lux), was used as a proxy for outdoor exposure while other readings captured during waking hours were categorized as indoor exposure. The daily mean of white and colored (RGB) light intensity was calculated for both in- and outdoors.
Myopes had less mean daily white light exposure compared to non-myopes (mean & range of difference: 244 lux, 826-915), which was primarily due to differences in outdoor exposure (495 lux, 959-1296 lux). The outdoor:indoor ratio for each RGB intensity was ~20:1 for myopes compared to 3:1 for non-myopes. The red:green exposure ratio was lower for myopes compared to non-myopes while indoors (1.66 vs. 2.53), but similar when outdoors (1.64 vs. 1.66). There was no apparent difference in the blue:green exposure ratio for myopes and non-myopes when indoors or outdoors. Interestingly, myopes experienced slightly less red:blue exposure when indoors (2.57 vs. 2.78), but slightly more when outdoors (3.31 vs. 3.04). Outdoor spectral exposure differences may reflect group differences in behavior; non-myopes recorded multiple short morning outdoor exposures and longer noon/afternoon exposures while myopes had multiple short afternoon-dusk exposures, with longer exposures randomly distributed across the day.
Results suggest that differences in outdoor activities and thus light exposure between myopes and non-myopes persist outside the academic year. Wavelength-related differences in indoor ambient light exposure were an unexpected observation. Further work is warranted to investigate the origin of this difference (e.g. device use) and the significance of differences in temporal patterns of outdoor exposure, as suggested by the above data, for myopia development and/or progression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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