Associations between axial length, corneal refractive power and lens thickness in children and adolescents: The Ural Children Eye Study

Purpose: To assess relationships between ocular biometric parameters in dependence of age and sex in children and adolescents. Methods: In the Ural Children Eye Study, a school-based cohort study, 4933 children underwent an ophthalmological and general examination. Results: Complete biometric measurements were available for 4406 (89.3%) children. Cycloplegic refractive error (mean: - 0.87 +/- 1.73 diopters (D); median: -0.38 D; range: -19.75 D to +11.25 D) increased (multivariable analysis; r(2) = 0.73) with shorter axial length (beta: -0.99; non-standardized regression coefficient B: -1.64; 95% CI: -1.68, -1.59) and lower corneal refractive power (beta: -0.55; B: -0.67; 95% CI: -0.70, -0.64), in addition to higher cylindrical refractive error (beta: 0.10; B: 0.34; 95% CI: 0.27, 0.41), thinner lens (beta: -0.11; - 0.85; 95% CI: -1.02, -0.69) and male sex (beta: 0.15; B: 0.50; 95% CI: 0.42, 0.57). In univariate analysis, decrease in refractive error with older age was more significant (beta: -0.38 vs. beta: -0.25) and steeper (B: -0.22 (95% CI: -0.24, -0.20) vs. B: - 0.13 (95% CI: -0.15, -0.11)) in girls than boys, particularly for an age of 11+ years. Axial length increased with older age (steeper for age <11 years) (B: 0.22 (95% CI: 0.18, 0.25) vs. 0.07 (95% CI: 0.05, 0.09)). In multivariable analysis, axial length increased with lower refractive error (beta: -0.77; B: -0.42; 95% CI: -0.43, -0.40) and lower corneal refractive power (beta: -0.54; B: -0.39; 95% CI: - 0.41, - 0.38), in addition to older age (beta: 0.04; B: 0.02; 95% CI: 0.01, 0.03), male sex (beta: 0.13; B: 0.23; 95% CI: 0.21, 0.32), higher cylindrical refractive error (beta: 0.05; B: 0.09; 95% CI: 0.05, 0.14) and thinner lens (beta: -0.14; B: -0.62; 95% CI: -0.72, -0.51). The axial length/ corneal curvature (AL/CR) ratio increased until the age of 14 years (beta: 0.34; B: 0.017; 95% CI: 0.016, 0.019; p < 0001), and then became independent of age. The AL/CR ratio increased (r2 = 0.78) mostly with higher corneal refractive power (beta: 0.25; B: 0.02; 95% CI: 0.02, 0.02; p < 0.001), lower refractive error (beta: -0.75; B: -0.05; 95% CI: -0.05, -0.05; p < 0.001), thinner lens thickness (beta: -01.6; B: -0.09; 95% CI: -0.10, -0.08; p < 0.001) and older age (beta: 0.16; B: 0.006; 95% CI: 0.005, 0.007; p < 0.001). Conclusions: In this multiethnic group of school children in Russia, the age-related increase in myopic refractive error was more significant and steeper in girls, particularly for the age group of 11+ years. Determinants of higher myopic refractive error were longer axial length, higher corneal refractive power, lower cylindrical refractive error, thicker lens and female sex.