Abstract
Purpose :
Previous work by our lab has shown that both scotopic and photopic ambient lighting is protective for lens-induced myopia (LIM) in wild-type mice (Landis et al., IOVS 2021). Evidence suggests that both mouse rod and cone photoreceptors can detect photopic lighting (Tikidji-Hamburyan et al., Nat Commun 2017). To investigate the origins of the protective effect of photopic lighting in myopigenesis, we measured the response to LIM in transgenic mice with rod-only retinas exposed to different ambient light levels.
Methods :
Rod, cone, and melanopsin photoreceptors were targeted using Gnat1+/+, Gnat2-/-, Opn4-/- mice, respectively, creating mice with rod-only retinas. Mice were used as naïve controls (control, n=20) or received a monocular -10 D lens over the right eye (LIM, n=21). Animals were placed in one of three ambient lighting conditions: 1 lux (scotopic, n=14), 50 lux (mesopic, n=13), or 10,000 lux (photopic, n=14) on a 12:12 light:dark cycle. Refractive errors, corneal curvature and ocular axial parameters were tested at baseline, 1- and 2-weeks post-goggling using an automated photorefractor, keratometer, and SD-OCT. Myopic shifts were calculated as the difference in refractive error between the right and left eyes.
Results :
Myopigenesis occurred in all LIM mice over the treatment period, while no myopia developed in control mice (0.02±0.39D). However, the degree of myopigenesis was influenced by light levels (p<0.001). LIM mice exposed to ambient 50 lux and 10,000 lux lighting developed comparably severe myopic shifts, (-5.90±0.42 D and -6.68±0.49 D, respectively, p=n.s.). In contrast, LIM mice exposed to ambient 1 lux lighting developed significantly less myopic shift compared to the mice in 50 and 10,000 lux lighting (-3.97±0.35 D, p<0.01). Other measured outcomes did not change with LIM or light exposure.
Conclusions :
Here, we exploited a transgenic mouse model with intact rod, but disrupted cone and melanopsin, signaling to determine which photoreceptor pathways underlie the protective effect of photopic lighting in LIM. Our results indicate that a rod-only retina provided the needed signaling for the protective effects of scotopic lighting during LIM, while not contributing to the protective effect of photopic lighting for myopic eye growth. Future studies will examine the effects of a cone only retina on LIM under different ambient light levels.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.