[Age dependent refractive compensation for axial elongation in children modulated by follow-up duration and myopic status].

Objective: To investigate age-related dynamics of refractive compensation for axial elongation in children aged 6-9 years, and examine the modulating effects of follow-up duration, baseline age, and refractive status. Methods: This prospective cohort study analyzed data from the Shanghai Time Outside to Reduce Myopia Trial (2016-2020), including 1 805 non-myopic or low-myopic children [mean age (6.77±0.35) years; 52.0% male]. Quantile regression analysis characterized spherical equivalent changes (ΔSE) per millimeter of axial elongation (ΔAL) across different observation periods (1-4 years). Mixed-effects models evaluated moderating factors including age and baseline refractive status. Results: Axial elongation demonstrated strong positive correlations with refractive changes across all follow-up durations (r:0.79-0.91, P<0.001). The median refractive compensation per millimeter axial elongation exhibited significant temporal attenuation: 2.06 D (1.84-2.31 D) at 1-year follow-up decreasing to 1.50 D (1.25-1.75 D) over 3-4 years (P-trend<0.001). Each additional baseline year reduced compensation magnitude by 0.19-0.31 D (P<0.05), with 6-year-olds showing 30.1% reduction in compensation efficiency (2.06 -1.44 D) over 4 years. Non-myopic eyes demonstrated 28.0% lower baseline compensation (1.44 D vs. 2.00 D, P<0.001) with slower annual attenuation (0.03 D vs. 0.19 D) compared to myopic eyes. Conclusions: Pediatric refractive compensation follows a dual attenuation pattern modulated by both age and time, with more pronounced compensation loss in myopic eyes. These findings emphasize the necessity for dynamic adjustment of axial length-to-refraction conversion formulae incorporating follow-up duration, baseline age, and refractive status to enhance myopia progression risk assessment.