Safety of Repeated Low-Level Red-Light Therapy for Myopia: A Systematic Review

TopicExisting evidence for the safety of repeated low-level red-light (RLRL) therapy for myopia control. Clinical relevanceRecent trials show RLRL therapy is effective in the prevention and control of myopia. Establishing its safety profile is necessary prior to widespread clinical implementation. MethodsWe conducted a systematic review (International Prospective Register of Systematic Reviews, CRD42024516676) of articles across seven databases from inception through February 10, 2024, with keywords related to myopia and RLRL therapy. Pooled safety outcomes and risk-to-benefit ratios were reported, and incidence of side effects was compared with other anti-myopia interventions. Quality appraisal was performed using the Cochrane Risk of Bias Tool. ResultsAmong 689 screened articles, 20 studies (2.90%; eleven randomized controlled trials, four non-randomized controlled trials, one post-trial study, one single-arm study, one retrospective study and two case reports of identical patient.; median duration 9 months, longest 24 months) were analysed, encompassing 2,380 participants aged 3-18 years and 1,436 individuals undergoing RLRL therapy. Two case reports described an identical patient with reversible decline in visual acuity and optical coherence tomography (OCT) abnormalities, completely resolved 4 months after treatment cessation. No cases of permanent vision loss were reported. Temporary afterimage was the most common ocular symptom following treatment, resolving within 6 minutes in reported studies. The number needed to harm outweighed the number needed to treat by a ratio of 12.7-21.4 for a person with -3D to -8D myopia treated with RLRL therapy. Incidence of side effects from RLRL was 0.088 per 100 patient-years (95% confidence interval [CI], 0.02-0.50), comparable to spectacles designed for myopia reduction (0.22; 95% CI, 0.09-0.51; P=0.385), and significantly lower than for low-dose atropine (7.32; 95% CI, 6.65-8.05; P<0.001), orthokeratology (20.6; 95% CI, 16.7-25.0; P<0.001), other anti-myopia contact lens (19.3; 95% CI, 17.6-21.1; P<0.001). ConclusionNo irreversible visual function loss or ocular structural damage was identified with RLRL. Fundus photography and OCT before and during therapy, alongside home monitoring of visual acuity and duration of afterimages, are necessary to identify side effects. Further adequately-powered studies of longer duration are needed to evaluate long-term safety of RLRL.