medwireNews: Repeated low-level red light (RLRL) therapy used to control myopia progression in children may be associated with cellular-level changes in the retina, specifically reduced cone photoreceptor density, according to a cohort study published in JAMA Ophthalmology.
“[F]urther studies are needed to provide more definitive information regarding longer-term efficacy and safety,” of the therapy, state the authors.
For the retrospective multicenter study, Kai Wang, from Peking University People’s Hospital in Beijing, China, and colleagues collated data between January and March 2024 on 99 Chinese children aged 5–14 years. All the children had myopia, defined as a spherical equivalent refraction below −6.00 diopters, and best-corrected visual acuity of 20/20 or better.
A total of 52 children (97 eyes; mean age 10.3 years; 51.9% female) formed the RLRL group – all had used daily RLRL therapy for at least 12 months with registered devices operating at 0.2 to 2.0 mW laser power. The remaining 47 children (74 eyes; mean age 9.8 years; 46.8% female), who had never used the treatment, formed the control group. The two groups were well matched at baseline, with no significant differences in age, sex, spherical equivalent refraction, mean macular thickness, or ocular axis length.
The team assessed retinal structure using adaptive optics scanning laser ophthalmoscopy (AOSLO) – a high-resolution imaging technique that allows the measurement of cone density in vivo. The study’s primary outcomes focused on cone photoreceptor density measured along four retinal meridians from the central fovea to 4° eccentricity, with additional outcomes including assessment of fundus abnormalities using AOSLO, optical coherence tomography (OCT), and fundus photography.
Compared with nonusers, children who had undergone RLRL therapy had decreased cone density within 0.5 mm eccentricity from the foveal center, and most notably at 0.3 mm from the temporal region where there was a mean 2.1 × 10³ cells/mm² reduction compared with controls.
Additionally, a total of 11 eyes (from 10 participants) exhibited abnormal low-frequency, high-brightness signals near the fovea. These occurred in the eyes of seven long-term RLRL users (>12 months), three short-term RLRL users (<12 months), and one nonuser, translating to a 7.23-fold increased risk among RLRL users. The authors note these abnormal signals resemble early drusen-like changes – subretinal deposits typically associated with age-related macular degeneration.
“Although minimal drusen may occur in normal eyes, their increased prevalence in RLRL users warrants attention,’ they say.
One child in the RLRL group showed cystoid cavities in the ganglion cell layer on OCT imaging that resolved after the therapy was discontinued for 3 months. Although baseline OCT images were not available, the authors comment that this case “suggests that RLRL therapy may be associated with different retinal layers, potentially exceeding tissue tolerance limits.”
In conclusion, the authors highlight the need for further studies “to determine a causal relationship and whether these retinal changes are progressive or stabilized.”
In a commentary accompanying the study, Jacque Duncan, from the University of California in San Francisco, USA, notes the potential public health implications of these findings given the global rise in myopia and growing interest in light-based therapies.
However, she cautions that the study was small, not randomized, and patients were not studied longitudinally. The commentator also raised the fact that a family history of high myopia or myopic degeneration as a confounding factor was not accounted for.
Despite these limitations, Duncan agrees that the study “provides evidence that RLRL may have subtle effects on cone density that are not readily visualized with standard clinical tests,” and calls for future randomized trials to incorporate high-resolution imaging at baseline.
“[S]tudies of retinal structure and function beyond 12 months are needed to determine if RLRL is a safe and effective intervention to prevent myopia progression,” she concludes.
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JAMA Ophthalmol 2025; doi:10.1001/jamaophthalmol.2025.0957
JAMA Ophthalmol 2025; doi:10.1001/jamaophthalmol.2025.0835
