This article was originally published in a sponsored newsletter.
The understanding of myopia progression and management continues to evolve, and advancements in this field are promising. Research focused on slowing progression and preventing onset contributes to our armamentarium for myopia management.
Evidence indicates that myopic defocus retards myopia while the opposite occurs with hyperopic defocus.1 In addition, longer-wavelength light focuses posterior to shorter-wavelength light, thus inducing a relative hyperopic defocus compared to a shorter wavelength.1 Results from some initial experiments suggested that blue light might be helpful in slowing myopia, which supports this hypothesis.1 However, the opposite was found in later experiments in which blue light promoted progression and red light retarded myopia.1
The safety and efficacy of repeated low-level red light (RLRL) in managing myopia has been demonstrated repeatedly. Compared to control and sham treatment groups, myopic children treated with RLRL showed smaller shifts in spherical equivalent and slower axial growth.2,3 Besides decelerating axial stretch and retarding progression in spherical equivalent, red light also induces sustained choroidal thickening, and choroidal thickness change at three months could predict the 12-month efficacy of red light therapy.4
A recent trial of red light therapy demonstrated its superior efficacy compared with 0.01% atropine during a 12-month period.5 Still, head-to-head trials comparing red light to other optical strategies (such as stronger concentrations of atropine) are lacking. Interestingly, all human trials on red light for myopia have been conducted with Chinese children. It is unknown, however, whether similar efficacy and safety can be achieved in other ethnic groups, although a recent editorial suggests that it would.6
The mechanism by which red light impedes ocular growth is not yet well understood. One possible explanation is that monochromatic red light is interpreted as a cue by emmetropization mechanism that the eye is too long and should slow its growth.7 Alternatively, photobiomodulation leading to the release of dopamine and nitric oxide also has been postulated.8
The understanding of the role of red light in myopia control is evolving. Based on current data, red light therapy appears to be an emerging option for managing myopia, but much remains to be learned: The optimum power, dose, and duration of red light; the effects of factors such as age, ethnicity, pupil size, and accommodation; and whether combining red light therapy with other myopia control strategies provides additional control. Furthermore, fully understanding the mechanism by which red light therapy slows down myopia will further our insights into emmetropization, myopia development and progression, and strategies to slow it.
1. Gawne TJ, Siegwart JT, Ward AH, Norton TT. The wavelength composition and temporal modulation of ambient lighting strongly affect refractive development in young tree shrews. Exp Eye Res. 2017 Feb;155:75-84.
2. Zhou L, Xing C, Qiang W, Hua C, Tong L. Low-intensity, long-wavelength red light slows the progression of myopia in children: an Eastern China-based cohort. Ophthalmic Physiol Opt. 2022 Mar;42:335-344.
3. Dong J, Zhu Z, Xu H, He M. Myopia Control Effect of Repeated Low-Level Red-Light Therapy in Chinese Children: A Randomized, Double-Blind, Controlled Clinical Trial. Ophthalmology. 2023 Feb;130:198-204.
4. Xiong R, Zhu Z, Jiang Y, et al. Longitudinal Changes and Predictive Value of Choroidal Thickness for Myopia Control after Repeated Low-Level Red-Light Therapy. Ophthalmology. 2022 Oct 11; S0161-6420(22)00780-1. [Online ahead of print]
5. Chen Y, Xiong R, Chen X, et al. Efficacy Comparison of Repeated Low-Level Red Light and Low-Dose Atropine for Myopia Control: A Randomized Controlled Trial. Transl Vis Sci Technol. 2022 Oct 3;11:33.
6. Bullimore MA, Brennan NA. Efficacy in Myopia Control: Does Race Matter? Optom Vis Sci. 2023 Jan 1;100:5-8.
7. Seidemann A, Schaeffel F. Effects of longitudinal chromatic aberration on accommodation and emmetropization. Vision Res. 2002 Sep;42:2409-2417.
8. Carr BJ, Stell WK. Nitric Oxide (NO) Mediates the Inhibition of Form-Deprivation Myopia by Atropine in Chicks. Sci Rep. 2016 Dec 5;6:9.