Abstract: Objective To investigate the diagnostic value of the axial length-to- corneal radius (AL/CR) ratio for assessing myopia in preschool children aged 3 to 6 years. Design A cross-sectional study. Participants Cluster sampling was used to select 1878 children aged 3 to 6 years from 27 kindergartens in Haidian District, Beijing from December 2020 to August 2021. Methods After cycloplegia, refraction was measured in both eyes to determine the spherical equivalent (SE). Axial length (AL) and corneal curvature (K) were measured using optical biometry, with the corneal radius (CR) and the axial length-to-corneal radius ratio (AL/CR) calculated. Myopia was defined as SE≤-0.50 D, and AL/CR>3 was considered indicative of suspected myopia. Data were analyzed using normality tests, rank correlation analysis, and receiver operating characteristic (ROC) curves to evaluate the predictive value of AL/CR for myopia in children aged 3 to 6 years. Main Outcome Measures SE, AL/CR , sensitivity, specificity , and the area under the ROC curve. Results Both SE and AL/CR values followed a normal distribution, with average SE at (1.15±0.94) D and average AL/CR at (2.86±0.07). Correlation analysis revealed a negative association between SE and AL/CR (r=-0.324, P＜0.01). Compared with the results from cycloplegic refraction(SE≤-0.50 D), the sensitivity of the AL/CR ratio >3 for diagnosing myopia was 0.375, with a specificity of 0.985, an accuracy of 95.7%, and a Kappa coefficient of 0.956. The area under the ROC curve was 0.862. At an AL/CR cutoff of 2.928, the Youden index was maximized, yielding a sensitivity of 73.90% and a specificity of 85.30% for diagnosing myopia. Conclusion The AL/CR ratio demonstrates high specificity and accuracy in diagnosing myopia in preschool children, indicating its significant clinical value for predicting the onset of myopia. (Ophthalmol CHN, 2025, 34: 36-39)

Key words: myopia, preschool children, axial length, AL/CR ratio, ROC curve