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

Abstract 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 ( β : −0.99; non‐standardized regression coefficient B : −1.64; 95% CI: −1.68, −1.59) and lower corneal refractive power ( β : −0.55; B : −0.67; 95% CI: −0.70, −0.64), in addition to higher cylindrical refractive error ( β : 0.10; B : 0.34; 95% CI: 0.27, 0.41), thinner lens ( β : −0.11; −0.85; 95% CI: −1.02, −0.69) and male sex ( β : 0.15; B : 0.50; 95% CI: 0.42, 0.57). In univariate analysis, decrease in refractive error with older age was more significant ( β : −0.38 vs. β : −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 ( β : −0.77; B : −0.42; 95% CI: −0.43, −0.40) and lower corneal refractive power ( β : −0.54; B : −0.39; 95% CI: −0.41, −0.38), in addition to older age ( β : 0.04; B : 0.02; 95% CI: 0.01, 0.03), male sex ( β : 0.13; B : 0.23; 95% CI: 0.21, 0.32), higher cylindrical refractive error ( β : 0.05; B : 0.09; 95% CI: 0.05, 0.14) and thinner lens ( β : −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 ( β : 0.34; B : 0.017; 95% CI: 0.016, 0.019; p < 0001), and then became independent of age. The AL/CR ratio increased ( r 2 = 0.78) mostly with higher corneal refractive power ( β : 0.25; B : 0.02; 95% CI: 0.02, 0.02; p < 0.001), lower refractive error ( β : −0.75; B : −0.05; 95% CI: −0.05, −0.05; p < 0.001), thinner lens thickness ( β : −01.6; B : −0.09; 95% CI: −0.10, −0.08; p < 0.001) and older age ( β : 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.