Efficacy of 50 % vs. 100 % intensity repeated low-level red-light on choroidal thickness and vasculature: A randomized crossover trial.

PURPOSE: To determine if 50 % repeated low-level red-light therapy (RLRL) can achieve the same choroidal thickening as the standard 100 % intensity, potentially reducing energy use without sacrificing efficacy in myopia control. This study aimed to investigate the daily choroidal thickness (ChT) and vasculature, as surrogate outcomes for myopia control efficacy, with the RLRL at 100 % and 50 % intensity.

METHODS

This prospective crossover randomized controlled trial recruited adults aged 18-40 years with myopia. The study consisted of two 4-week treatment phases separated by a 4-week washout period, with participants randomly assigned to either a 100 %-50 % or 50 %-100 % RLRL treatment sequence. The primary outcomes were changes in subfoveal ChT (sfChT) and mean macular ChT (mChT) measured daily using swept-source optical coherence tomography. Secondary outcomes included macular choroidal vasculature.

RESULTS

The study included 27 participants (mean age, 21.2 years). After 1 month of treatment, both 50 % and 100 % RLRL resulted in significant increases in sfChT, mChT, and peripapillary ChT, with no significant differences between the two groups. Choroidal thickening developed gradually over the treatment period, and daily change profiles in ChT and vasculature parameters were comparable.

CONCLUSIONS

This study demonstrates that both 50 % and 100 % RLRL produced similar choroidal thickening, suggesting that 50 % RLRL may offer comparable myopia control efficacy with reduced energy usage.