Sustained Effect of Red-light Therapy for Myopia Control: A 2-Year Post-Trial Follow-up Study

To evaluate the long-term efficacy and safety of red-light therapy for myopia control over 2 years, and the potential rebound effect after treatment cessation. The Chinese myopic children who originally completed the one-year randomised controlled trial in the previous study were enrolled. Children continued or started to daily usage of red-light therapy were defined as the RL group, while those who stopped using red-light therapy and switched to single-vision spectacles (SVS) as well as those who continued to keep single-vision spectacles in the second year were both regarded as the SVS group. Red-light 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. Changes in axial length (AL) and cycloplegic spherical equivalence refraction (SER) are to be measured and compared as well as the adverse effects including the rebound effect. Red-light therapy has emerged as a novel myopia control treatment modality recently. A 12-month randomised controlled trial (RCT) conducted by our research team was thought to be earlier to evaluate the treatment of myopic children using red-light therapy. The trial demonstrated that PBM therapy was effective on myopia control, reducing axial elongation and spherical equivalence refraction (SER) progression 103% and 127% compared with single vision spectacle (SVS) over a 12-month period, respectively. The promising efficacy of red-light therapy has been further confirmed in other studies. In addition, satisfactory user acceptability and no unrecovered functional and structural damages were observed. Myopia generally progresses throughout childhood and hence a study duration of 1 year is not sufficient to widely adopt the red-light therapy as a treatment strategy for myopia control. The sustainability of treatment efficacy, rebound phenomenon upon cessation of treatment, and potential risks and adverse effects in myopic children with longer-term PBM therapy, remain to be fully elucidated. Thus, the aims of this post-trial follow-up study were to invite the participants to come back for a 24-month visit and to investigate the long-term efficacy and safety of continued red-light therapy as well as the potential rebound effect following red-light treatment cessation.