Evaluating the Effect on Emmetropization of the Timing and Spectrum of Breaks From a Myopiagenic Environment

Purpose: Here, we use a tree shrew model of slowly progressing childhood myopia to evaluate how regular breaks from a myopiagenic visual environment affect the development of myopia. Methods: At 24 days of visual experience (DVE), 36 tree shrews were exposed to myopiagenic ambient light consisting of limited-bandwidth blue and cyan, which was then interrupted by various patterns and durations of white or narrowband red ambient light. Seven animals raised in colony lighting served as controls. Refractions at 100 DVE were compared across the groups. Results: Relative to emmetropic controls, animals raised in blue + cyan light showed a gradual myopic shift (-4.7 ± 0.9 SEM diopters [D] at 100 DVE, P < 0.001). For white light, 20-second breaks every 20 minutes were ineffective in preventing myopia (-5.9 ± 2.3 SEM D, P = 0.004). Both 5-minute (-1.5 ± 0.2 SEM D) and 10-minute (-1.1 ± 0.1 SEM D) white-light breaks every 20 minutes were only partially effective. Narrowband red light for 10 minutes every hour induced significant hyperopia (+4.4 ± 0.6 SEM D). Despite relatively higher variance, red light 10 minutes every 2 hours and 20 minutes twice a day also inhibited myopia (+1.1 ± 1.3 and -0.8 ± 1.3 SEM D). Conclusions: While white-light breaks were relatively ineffective in inhibiting myopia, data showed that short breaks with ambient red light can be very effective if of an appropriate kind. The results suggest that using breaks from myopiagenic activity to stop or slow myopic progression depends critically on both the timing and nature of the breaks.