Correlations among Refractive Error, Axial Length, and Corneal Power in Childhood

Purpose: To investigate sexual differences and correlations among refractive error, axial length (AL), and corneal power. Methods: A retrospective review of the medical records for 2,006 eyes of children aged 5-16 years was conducted. Cycloplegic refraction and AL measurements were performed on all eyes. Sexual differences in corneal power and AL were investigated in emmetropic eyes and after adjustment for the spherical equivalent (SE). The distribution of AL with every 1 diopter (D) interval was determined. Quantitative correlations among SE, corneal power, and AL were analyzed using multiple regression analyses. Results: The mean age of the subjects was 7.62 years and the mean SE was -0.10 D. Males had a longer AL and lower corneal power than females both in emmetropic eyes and in all subjects after adjustment for the SE. The AL increased 0.40 mm for every -1 D change of the SE. When compared to a 1 D interval of the SE, the AL difference between the upper and lower values of a 95% confidence interval was 2.98 mm, which showed the variability of the AL distribution. Eyes with a long AL had lower corneal power (p < 0.001). Every 1 mm change of AL resulted in a -2.1 D change in the SE, and every 1 D change of corneal power resulted in a -0.8 D change in the SE (p < 0.001). Conclusions: The distribution of the AL and corneal power was variable, even in eyes with the same refractive error. The AL and corneal power differed by sex. Quantitative correlations between the SE, AL, and corneal power can be clinically used in the estimation of these parameters.