The Effects of Repeated Low-Level Red-Light Therapy on the Structure and Vasculature of the Choroid and Retina in Children with Premyopia

Introduction: The purpose of this study was to explore the effects of repeated low-level red-light (RLRL) therapy on the structure and vasculature of the choroid and retina in Chinese children with premyopia.Methods: This study was a single-center randomized clinical trial. A total of 94 children with premyopia (- 0.50 D < spherical equivalent [SE] <= + 0.75 D) were randomly assigned to either the RLRL therapy or control group. Follow-up visits were planned at 1, 3, 6, 9, and 12 months. Optical coherence biometry was used to measure axial length (AL) and anterior segment parameters. Choroidal thickness (CT), retinal thickness (RT), superficial retinal vascular density (SRVD), deep retinal vascular density (DRVD), choriocapillaris perfusion area (CCPA), and choroidal vessel volume (CVV) were measured by optical coherence tomography angiography, centered on the foveal, parafoveal (ParaF), and perifoveal (PeriF) regions.Results: The thickening of the choroid was observed across the entire macular region at different time points in the RLRL therapy group. Relative to the baseline measurement, foveal CT significantly increased at the 1-month follow-up with RLRL therapy, with a mean (+/- standard deviation [SD]) adjusted change of 16.96 +/- 19.87 mu m. The greatest magnitude of foveal CT changes was observed at the 3-month visit (an increase of 19.58 +/- 20.59 mu m), with a slight reduction in the extent of foveal CT increase at the 6-month visit (an increase of 15.85 +/- 23.77 mu m). The second greatest CT increase was observed at the 9-month visit (an increase of 19.57 +/- 35.51 mu m), after which the extent of CT increase gradually decreased until the end of the study at the 12-month visit (an increase of 11.99 +/- 32.66 mu m). We also observed a significant increase in CT in the ParaF and PeriF areas in the RLRL group over 12 months. In contrast, CT across the entire macular region in the control group significantly decreased throughout the follow-up visits (all P < 0.05). Regarding the vascular parameters of the choroid, significant increases in CVV were observed primarily in the ParaF and PeriF regions of the choroid in the RLRL group. In comparison, the control group exhibited decreases in CVV throughout the entire area. Furthermore, notable elevations in CCPA were detected in the PeriF area of the choroid in the RLRL group during the 1-month (an increase of 0.40 mm(2)), 3-month (an increase of 0.25 mm(2)), and 12-month visits (an increase of 0.42 mm(2)) (all P < 0.05). In addition, no notable differences were observed between the groups regarding foveal RT and retinal vascular parameters throughout the 12 months (P > 0.05). Notably, RLRL therapy achieved a notable reduction in SE shift by 73.8%, a substantial decrease in AL change by 67.9%, and a significant reduction in myopia incidence by 45.1% within 1 year.Conclusion: Our study demonstrated a significant increase in CT and flow in the RLRL-treated eyes throughout the 12-months of the study. Combined with its reduction in spherical equivalent progression and axial elongation, RLRL could be used as an effective therapy for preventing progression in premyopes.