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Research Article: Age-indexed cumulative risk of high myopia estimated from axial length and early axial elongation: a 7-year school-based longitudinal cohort study

Date Published: 2026-10-05

Abstract:
To develop and validate age-indexed models estimating the cumulative risk of high myopia, defined as axial length (AL)???26.0?mm, using routinely collected ocular biometry, and to evaluate their potential for clinical risk stratification. This 7-year school-based longitudinal cohort included 7,052 Chinese children aged 6–16 years at baseline who participated in a school-based screening program in Tianjin, China, from 2018 to 2024. Discrete-time survival models with age as the timescale estimated cumulative risk from ages 9 to 18 years. Two models were tested: baseline AL plus sex and baseline AL plus first-year axial elongation (?AL) plus sex. Performance was assessed in a participant-level temporal holdout test set using iAUC, iBrier, calibration, and decision-curve analysis, and by school-level internal-external cross-validation using iAUC and iBrier. Overall, 577 participants (8.2%) developed high myopia. In the temporal holdout test set ( n =?5,245), the AL?+??AL model outperformed the AL-only model, with higher discrimination [iAUC, 0.919 [95% CI, 0.902–0.933] vs. 0.851 [95% CI, 0.833–0.869]] and lower prediction error [iBrier, 0.074 [95% CI, 0.068–0.081] vs. 0.087 [95% CI, 0.080–0.095]]. Calibration was close to ideal, decision-curve analysis showed clinical net benefit, and school-level validation confirmed stable performance. Routine AL measurement, particularly when combined with early axial elongation, enables accurate age-specific risk estimation of AL-defined high myopia and provides a transparent basis for timely and proportionate myopia-control decisions.

Introduction:
Myopia is a major global public health concern, particularly among children and adolescents. Recent estimates indicate that the prevalence of myopia in this demographic has risen from 24.32% in 1990 to 35.81% in 2023, with projections reaching 39.80% by 2050, affecting over 740 million individuals worldwide ( 1 ). For the overall population, approximately 50% are projected to be myopic and about 10% to have high myopia by 2050 ( 2 ). High myopia is associated with sight-threatening complications, including myopic…

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