To evaluate the effectiveness and safety of RLRL in delaying the progression of high myopes -6.00 D or worse.Multicenter, randomized, parallel-group, single-blind clinical trial.Two hundred and two high myopic children aged 7 to 12 years with cycloplegia spherical equivalent refraction (SE) ≤ -6.00 D, astigmatism less than 2.50 D, anisometropia of 1.50 D or less were enrolled from March 2022 to December 2022. Follow-up was completed in December 2023.Eligible participants were randomly allocated to either the intervention (RLRL + single vision spectacle [SVS]) or the control group (SVS). The RLRL treatment was administered every day for 3 minutes, twice a day, with an interval of at least 4 hours.The primary outcome was the change in axial length (AL) at 12 months compared to baseline. Secondary outcomes included changes in SE, changes of choroidal thickness (ChT) and retinal thickness (RT) in different circle sectors. Outcomes were analyzed by means of intention-to-treat and per-protocol methods.After 12-month treatment, AL and SE changes were -0.11 ± 0.25 mm and 0.18 ± 0.63 D for RLRL group and 0.32 ± 0.09 mm and -0.80 ± 0.42 D for control group. Axial shortening > 0.05 mm was observed to 59% in the RLRL and 0% in the control group at 12 months. ChT and RT from a single center were analyzed. In the RLRL group, ChT were thickened in all sectors at 12 months. RT was increased in parafoveal and perifoveal circles. In the control group, all sectors of ChT and only perifoveal RT were significantly thinner at 12 months. The multivariate linear regression model revealed significant correlations between changes in ChT central foveal circle and RT perifoveal circle at 1 month and AL changes at 12 months. No fundus structure changes, afterimage exceeding 6 minutes nor best corrected visual acuity decreased reported.RLRL could effectively shorten the AL and inhibit the progression of myopia in high myopic patients -6.00 D or worse. AL shortening is sustained over 12 months of treatment. These observed changes appeared to be associated with increases in ChT and RT.Copyright © 2024. Published by Elsevier Inc.