Although the mechanism behind remains unclear, many clinical trials have demonstrated its effectiveness in managing the rate of myopia progression in myopic children and the risk of myopia onset in pre-myopic children by several randomized controlled trials (RCTs).

For myopic children, the first multi-center single-blind RCT of RLRL was conducted in 2019. In this 12-month result, RLRL treatment slowed axial elongation by 0.26 mm and SER progression by 0.59 diopter compared with single-vision spectacle (SVS) group, representing a 69.4% and 76.6% slowing of axial elongation and myopic refraction progression, respectively(12).

A continuation real-world study of this RCT explored the long-term efficacy and safety of continued RLRL therapy on myopia control over 2 years in children aged between 8 and 13 years. For those who continued RLRL for over 2 years, there was a 75% reduction in both AL and SER observed, with the smallest change in axial elongation and SER progression of 0.16±0.37mm and -0.31±0.79D respectively, compared to the highest increase in the single-vision spectacle (SVS)  group (0.64±0.29 mmand -1.24±0.63D respectively; p< />(13). For those who discontinued treatment in the second year, there was a modest rebound effect observed after treatment cessation. Similarly, Tian et al. reported notable differences in the median 6-month AL changes between the RLRL group and the control group, showing reductions of −0.06 mm (IQR −0.15, 0) compared to increases of 0.14 mm (IQR 0.07, 0.22; p < 0.001)="" />

Impact on Axial Length

Furthermore, studies have found that RLRL treatment not only slows down the increase in axial length, which is directly associated with myopia progression, but in some cases, it can even shorten the axial length. This reduction is particularly significant because axial lengthening is a primary factor in the worsening of myopia over time. A post-hoc analysis of the previous RCT by Jiang et al(12) found the frequency of axial length shortening > 0.05 mm was 21.9% in 12-month RLRL treatment, while the frequency of this amount of shortening was 1.38% in the control group(14). Although all choroidal parameters studied (luminal area, stromal area, total choroidal area, choroidal vascularity index) increased in the RLRL group and reduced in the control group(15), OCT examination confirmed that choroidal thickening only explained 28.3% of the AL shortening, indicating that true scleral remodeling or shortening may involve the observed AL shortening as response to RLRL(14).

Reference

12. Jiang Y, Zhu Z, Tan X, Kong X, Zhong H, Zhang J, et al. Effect of Repeated Low-Level Red-Light Therapy for Myopia Control in Children. Ophthalmology. 2022 May;129(5):509–19.

13. Xiong R, Zhu Z, Jiang Y, Kong X, Zhang J, Wang W, et al. Sustained and rebound effect of repeated low‐level red‐light therapy on myopia control: A 2‐year post‐trial follow‐up study. Clin Experiment Ophthalmol. 2022 Dec;50(9):1013–24.

14. Wang W, Jiang Y, Zhu Z, Zhang S, Xuan M, Tan X, et al. Axial Shortening in Myopic Children after Repeated Low-Level Red-Light Therapy: Post Hoc Analysis of a Randomized Trial. Ophthalmol Ther. 2023 Apr;12(2):1223–37.

15. Xuan M, Zhu Z, Jiang Y, Wang W, Zhang J, Xiong R, et al. Longitudinal Changes in Choroidal Structure Following Repeated Low-Level Red-Light Therapy for Myopia Control: Secondary Analysis of a Randomized Controlled Trial. Asia-Pac J Ophthalmol. 2023 Jul;12(4):377–83.