Sustained and rebound effect of repeated low-level red-light therapy on myopia control: A 2-year post-trial follow-up study

Abstract

Background: To evaluate the long-term efficacy and safety of continued repeated low-level red-light (RLRL) therapy on myopia control over 2 years, and the potential rebound effect after treatment cessation.

Methods: The Chinese myopic children who originally completed the one-year randomised controlled trial were enrolled. Children continued RLRL-therapy were defined as RLRL-RLRL group, while those who stopped and switched to single-vision spectacle (SVS) in the second year were RLRL-SVS group. Likewise, those who continued to merely wear SVS or received additional RLRL-therapy were SVS-SVS and SVS-RLRL groups, respectively. RLRL-therapy was provided by an at-home desktop light device emitting red-light of 650 nm and was administered for 3 min at a time, twice a day and 5 days per week. Changes in axial length (AL) and cycloplegic spherical equivalence refraction (SER) were measured.

Results: Among the 199 children who were eligible, 138 (69.3%) children attended the examination and 114 (57.3%) were analysed (SVS-SVS: n = 41; SVS-RLRL: n = 10; RLRL-SVS: n = 52; RLRL-RLRL: n = 11). The baseline characteristics were balanced among four groups. In the second year, the mean changes in AL were 0.28 ± 0.14 mm, 0.05 ± 0.24 mm, 0.42 ± 0.20 mm and 0.12 ± 0.16 mm in SVS-SVS, SVS-RLRL, RLRL-SVS and RLRL-RLRL group, respectively (p < 0.001). The respective mean SER changes were -0.54 ± 0.39D, -0.09 ± 0.55D, -0.91 ± 0.48D, and -0.20 ± 0.56D (p < 0.001). Over the 2-year period, axial elongation and SER progression were smallest in RLRL-RLRL group (AL: 0.16 ± 0.37 mm; SER: -0.31 ± 0.79D), followed by SVS-RLRL (AL: 0.44 ± 0.37 mm; SER: -0.96 ± 0.70D), RLRL-SVS (AL: 0.50 ± 0.28 mm; SER: -1.07 ± 0.69D) and SVS-SVS group (AL: 0.64 ± 0.29 mm; SER: -1.24 ± 0.63D). No self-reported adverse events, functional or structural damages were noted.

Conclusions: Continued RLRL therapy sustained promising efficacy and safety in slowing myopia progression over 2 years. A modest rebound effect was noted after treatment cessation.

Keywords: axial length; clinical trials; myopia control; repeated low-level red-light therapy; spherical equivalent refraction.

FIGURE 1

Study design and flow diagram of the post‐trial follow‐up study. The first year was the in‐trial period, after which time the randomization was stopped and all eligible participants were invited to voluntarily participate a real‐world study to use the RLRL therapy in the second year. Blue boxes indicate the in‐trial period. Green boxes indicate the post‐trial period. RLRL, repeated low‐level red‐light; SVS, single vision spectacle.

FIGURE 2

Mean changes in axial length and cycloplegic spherical equivalent refractions from baseline to 24 months. (A) For axial elongation; (B) for myopia progression. RLRL, repeated low‐level red‐light; SVS, single vision spectacle