Distribution of axial length in Japanese children and adolescents aged 4 to 19 years

PURPOSE: To investigate the distribution of axial length (AL) and the prevalence of long axial length (LAL) in Japanese children and adolescents. STUDY DESIGN: cross-sectional observational study METHODS: We analyzed AL data from 14,482 participants (7,457 boys and 7,025 girls) aged 4-19 in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study in Japan. AL was measured using a non-contact optical axis measurement device. We evaluated the distribution of AL in the participants with box plots for age. Segmented regression identified age-related trends and breakpoints. We calculated the age-specific proportions of participants with AL ≥ 24.5 mm and those with AL ≥ 26 mm, defined as LAL, which were considered indicative of suspected myopia. RESULTS: Mean AL increased with age, with a break point at 11.73 years. The slope before the break point was β = 0.27, while the slope after the break point decreased to β = 0.12. Boys showed earlier break point (9.87 years) than girls (15.91 years). Proportions with AL ≥ 24.5mm and ≥26mm began to increase approximately at 8 and 10 years of age respectively, with sex differences noted between ages 7 to 10 years and 10 to 11 years. CONCLUSION: This was the first large-scale AL survey in Japan and revealed the age and sex related distribution of AL and the proportion with LAL among Japanese children and adolescents aged 4 to 19 years.