Correlation between Baseline Axial Length and Myopia Progression Rate in Childhood

To evaluate the relationship between baseline axial length (AL) and the rate of myopia progression in children and determine whether baseline AL alone predicts rapid myopia progression.

This retrospective study included 1,458 patients (<20 years old) who underwent cycloplegic refraction and biometry for at least 2 years between 2011 and 2024. Myopia progression rate was assessed using AL elongation (mm/yr), spherical equivalent (SE) change (diopters/yr), and AL/K radius (AL/corneal radius per year). Partial correlation analysis and multiple linear regression were performed to assess linearity between AL and myopia progression rate.

A total of 2,916 eyes were analyzed. Baseline AL exhibited weak partial correlations with progression indicators. After adjusting for age, partial correlation coefficients for the right and left eyes were 0.297 and 0.305 for AL elongation, -0.267 and -0.278 for SE change, and 0.259 and 0.269 for AL/K radius rate, respectively. Multiple regression analyses, adjusting for age and K radius effect revealed that the linear model for the right and left eyes accounted for only 2.4% and 2.0% for AL elongation, 10.0% and 10.5% of SE change, and 1.5% and 1.3% of AL/K radius rate, respectively. Analysis using generalized estimating equations to account for inter-eye correlation revealed that AL had a minimal impact on myopic progression rates. Progression rates decreased with baseline AL >24 mm, suggesting a nonproportional relationship between AL and progression rate of myopia.

Baseline AL was not a linear independent predictor of rapid myopia progression. Myopia progression tended to be slow in patients with an AL >24 mm.