The Effect of Refractive Error and Time Spent Outdoors on Red and Blue Light-Driven Pupil Responses

Purpose: Outdoor activity is one of several factors identified as risk factors for myopia development. The retina’s exposure to bright light may be one of the features of being outside that contributes to this protective effect. Specialized cells in the retina, ipRGCs, are thought to control this process. Since pupillary responses to blue light have been a useful measurement of ipRGC activity related to refractive error in past studies, and ipRGC activity may also contribute to slowing eye growth and myopia through their connection with amacrine cells and release of retinal dopamine, we are investigating the effects of bright light exposure on pupillary responses in order to better understand the protective nature of outdoor time on myopia development.Methods: Ten non-myopic subjects were each assigned to spend a large amount of time outdoors (target = 12 hours total) for 5 days and a small amount of time outdoors (target = 2 hours total) for 5 days with at least 5 days of separation between the experimental time periods. Pupillary responses to alternating blue and red light, followed by red light, then blue light as single colors were measured at the initial visit and following each 5 day period. Data were compared to data from a similar previous study with 10 myopic subjects. Results: Subjects spent an average (±SD) of 0.74 ± 0.24 more log lux-minutes outdoors in the high light exposure compared to the low light exposure week (p