Effect of repeated Low-Level red light therapy on axial length in myopic individuals: predictors for a good response

Purpose: This study aimed to investigate the effects of Repeated Low-Level Red Light (RLRL) therapy on axial length (AL) in myopic individuals and to identify key predictors for a good response to the treatment, with a focus on baseline ocular characteristics and treatment compliance. Methods: A total of 91 participants were enrolled, with 50 classified in the poor responders' group and 41 in the good responders' group. Baseline characteristics, including age, gender, pupil constriction diameter (PCD), intraocular pressure (IOP), spherical equivalent refraction (SER), AL, corneal curvature (ACC), and choroidal thickness (CT) were recorded. Compliance and AL changes were tracked over one year. Univariable and multivariable analyses identified factors associated with AL changes. Results: Good responders' group showed a significant AL reduction (-0.29 ± 0.16 mm, p < 0.001), while poor responders' group had an increase (+ 0.23 ± 0.12 mm, p < 0.001). Good responders' group had lower initial SER (-4.15 ± 2.87 D vs. -2.62 ± 1.80 D, p = 0.004) and longer AL (24.76 ± 1.21 mm vs. 24.15 ± 0.99 mm, p = 0.010). Both groups showed CT changes (p < 0.001), with greater increases in good responders. Univariable analysis identified initial AL and SER as predictors of a good response (both p < 0.001). Compliance showed a trend toward significance in multivariable analysis (β = -0.196, p = 0.052). Conclusion: Longer baseline AL and lower SER are key predictors of a good response to RLRL therapy. Moreover, treatment compliance showed a trend toward significance, emphasizing its crucial role in achieving optimal outcomes.