Axial Length Growth Trajectories in Children Transitioning to Myopia

Purpose: To characterize axial length (AL) growth trajectories in children who developed myopia compared with children who remained nonmyopic. Design: Retrospective longitudinal cohort study. Participants: Clinical data from 895 Chinese children (aged 4-15 years at baseline) with nonmyopic refractive error (spherical equivalent refraction> –0.50 D) at baseline spanned at least 2 years. They were categorized into nonmyopic (n = 541) and incident myopia (n = 354) groups, based on whether they developed myopia (SE ≤ –0.50 D) during follow-up. Children in the incident myopia group contributed data to both premyopia onset and postmyopia onset stages. Methods: Right eye data were used for all analyses. Participants were classified as myopic based on the right eye's spherical equivalent refraction, regardless of the left eye status. AL was measured at multiple visits, and the rate of AL growth between visits calculated. Generalized estimating equations were used to model AL growth rate, accounting for within-subject correlations. Age, baseline AL, gender, and parental myopia were included as predictors in the model. Main Outcome Measures: Annual AL growth rate (mm/y). Results: Generalized estimating equations modeling revealed significant differences in AL growth rates; children in the postmyopia onset stage exhibited significantly faster AL growth compared to both the children in the premyopia onset stage and nonmyopic group (P < .001). This difference was most pronounced in younger children and diminished with age. Postmyopia onset AL growth was significantly faster than premyopia onset growth up to age 7 and the nonmyopic group up to age 10 (P < .05). All groups showed an age-related decline in AL growth rate, with the decline being most pronounced in children in the postmyopia onset stage, followed by the nonmyopic group, and then children in the premyopia onset stage Baseline AL was significantly associated with postmyopia onset AL growth rate (P < .001) but not with premyopia onset (P = .22) or nonmyopic (P = .07) growth rates. Neither gender nor parental myopia significantly impacted AL growth rate. Conclusions: AL growth accelerates significantly after myopia onset, particularly in children younger than 10. This underscores the need for prompt myopia control interventions in early-onset myopia.