Abstract
Purpose :
Increased exposure to bright outdoor lighting protects against myopic development in both animal and human studies. However, the typical experimental paradigm for animal studies starts the bright light exposure prior to or at the time of myopic induction. The objective of this study was to evaluate whether the protective effect of bright light was maintained when exposure occurred after the start of lens-induced myopia (LIM) in C57 mice.
Methods :
C57BL/6J mice were housed in bright ambient lighting (10,000 lux, 12:12 cycle) starting on post-natal day 23 (P23, pre-LIM, n = 9) or P30 (post-LIM, n = 7), and compared to mice housed in mesopic lighting (50 lux, 12:12 cycle) for the entirety of the experiment (mesopic, n = 7). On P28, LIM was induced by placing a -10D lens over the right eye (OD) in a subset of animals in each lighting group. Measurements of refractive error using photorefractometry, corneal curvature using keratometry, and ocular axial measurements from SD-OCT were taken at baseline, 1 week, and 2 weeks post-LIM. Three-way repeated measures ANOVA analysis was used to compared the effects of lighting, treatment, and age on each measurement taken.
Results :
Mice with lens defocus had significant myopic shifts (OD-OS) compared to naïve controls (p<0.05). The magnitude of the myopic shift was dependent on light exposure group. Mice exposed to bright light pre-LIM had significantly smaller myopia shifts (-3.63±0.50 D) compared to the mesopic group (-4.89±0.80 D, p<0.05). However, this protective effect was not maintained when exposure occurred post-LIM (-4.35±0.80 D, p>0.05). No significant differences were found between groups for corneal curvature or axial ocular parameters.
Conclusions :
Pre-LIM exposure to bright ambient lighting resulted in the expected reduction in myopic severity, but post-LIM exposure did not offer any protection against myopia. These results suggest that protective light may be most effective as a prophylactic treatment rather than a therapeutic treatment to slow further myopic development. Future research will focus on the mechanism(s) for the protective effect of photopic lighting and how its effectiveness changes with myopic induction.
This is a 2021 ARVO Annual Meeting abstract.