Axial Length Growth Reference Curves and LMS Parameters for Japanese Children and Adolescents Aged 4–20 Years: The TMM BirThree Cohort Study

PURPOSE: Although axial length (AL) growth reference curves exist for several populations, there are no AL growth reference curves or established methods for AL-for-age z-score calculation for Japanese children and adolescents. This study aimed to develop AL growth reference curves and lambda-mu-sigma (LMS) parameters for Japanese children and adolescents aged 4-20 years, enabling a standardised evaluation of ocular development in both clinical and research settings. METHODS: A cross-sectional analysis was conducted of the AL data from 14,482 children (7457 boys and 7025 girls) enroled in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study. Optical biometry was performed using 10 consecutive measurements per eye and the mean values used to reduce measurement variability. Participants with a history of ophthalmic diseases that could affect AL were excluded. The LMS method with a Box-Cox-Cole-Green distribution was used to construct smoothed references and estimate the LMS parameters using the gamlss package in R. RESULTS: Age- and sex-specific LMS values for the AL z-score calculation were provided at 0.1-year intervals to allow detailed age-specific assessment. Percentile and standard deviation curves were generated for each sex across the ages of 4-20 years. AL growth patterns in Japanese children were broadly comparable to those reported in other East Asian populations. CONCLUSION: The AL growth reference curves and LMS parameters established in this study offer a clinically relevant framework for evaluating ocular growth and monitoring myopia-related axial elongation in the Japanese paediatric population. These references contribute to early identification and intervention efforts in childhood myopia management and international comparisons.