Intermittent exposure to bright light can prevent form-deprivation myopia in a monkey model

Abstract

Purpose : To evaluate the impact of intermittent bright light exposure on ocular growth and refractive error development in a monkey model of form-deprivation myopia.

Methods : Eight infant macaques (21±4 days old) were housed for 210 days under a 12/12h light/dark cycle using standard fluorescent light (SL, 140 lux, 4000K). Macaques were assigned into 2 groups. Animals in group 1 (n=5, 2 rhesus, 3 cynomolgus) were raised under SL, whereas animals in group 2 (n=3, 2 rhesus, 1 cynomolgus) were exposed to an additional 4h/day of intermittent bright light (IBL). IBL consisted of 1h of high intensity LED light (11,066 lux, 4000K) delivered every 2h of SL. Form-deprivation myopia (FDM) was induced monocularly over 154 days using a custom-built 3D-printed helmet fitted with a plano lens and occlusion foil (20/300 VA) covering the form deprived (FD) eye. The fellow (control) eye was covered with a plano lens. Axial length (AL), refractive error and choroidal thickness were assessed fortnightly. Results are expressed as average inter-ocular difference (IOD= FD - control eye) ±SD. Outcome measures were compared between eyes on day 154 (D154) using a paired t-test and between groups using a Mann-Whitney U-test on areas under the outcome measures’ curves (AUC) across form-deprivation (D0 to D154).

Results : By the end of form-deprivation (D154), FD eyes exposed to SL had increased AL (IOD = +0.25±0.17 mm; P=0.03) and myopic refraction (IOD= -3.80±0.89 D; P<0.001), and thinner choroids (IOD= -11.8±5.72 µm; P=0.009) compared to control eyes. On the other hand, FD eyes exposed to IBL showed no changes in AL (IOD= +0.02±0.03 mm), refraction (IOD= +0.08±0.14 D) or choroidal thickness (IOD= -1.0±2.64 µm) (all P>0.05). Overall, across the form deprivation period, FD eyes exposed to IBL displayed reduced/abolished IOD in axial elongation, myopic refraction and choroidal thinning compared to the eyes exposed to SL (all P<0.05; Fig.1A-C).

Conclusions : Our preliminary findings suggest that 4h/day of IBL can prevent the development of FDM in infant macaques. Data from 5 additional animals are being collected and analyzed and will be presented at ARVO 2022.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1. IOD in AL, refraction, choroidal thickness compared between groups. Data from individual animals are plotted as thin light red and blue lines. Averaged data per group are plotted as thick red (SL) and blue (IBL) lines. *: P<0.05.