Relationship between the axial length/corneal radius of curvature ratio and hyperopia reserve in preschool children aged 3-6 years

Purpose This study aimed to investigate the association between the axial length (AL) to average corneal curvature (CR) ratio and hyperopia reserve in preschool children. Methods AL, CR, horizontal and vertical meridians of the corneal radius (CR1, CR2), and 1% atropine cycloplegic refraction were measured in preschool children aged 3 - 6 years. The corneal curvatures were then used to calculate the AL/CR1, AL/CR2, and AL/CR ratios. Results A total of 338 children were included, comprising 178 boys (52.7%) and 160 girls (47.3%). The mean values for AL, CR, AL/CR1, AL/CR2, AL/CR, and spherical equivalent refractive error (SER) were 22.11 +/- 0.88 mm, 7.77 +/- 0.26 mm, 2.80 +/- 0.09, 2.90 +/- 0.09, 2.85 +/- 0.09, and + 2.13 +/- 1.46 D, respectively. AL, AL/CR1, AL/CR2, and AL/CR increased with age, showing significant differences among age groups (P < 0.001). Conversely, SER moved from higher hyperopia toward lesser hyperopia with age, also showing significant differences among age groups (P < 0.001). Linear regression equations were established, with Y representing hyperopia reserve and X representing AL/CR: Age 3: Y = 44.67 - 15.02X; Age 4: Y = 33.96 - 11.19X; Age 5: Y = 42.11 - 13.98X; Age 6: Y = 44.94 - 15.00X. These results suggest that the AL/CR ratio could be used to assess hyperopia reserve insufficiency. The optimal cut-off point for the receiver operating characteristic (ROC) curve was >= 2.91, with a sensitivity, specificity, and Youden index of 0.84, 0.88, and 0.73, respectively. The critical value of the ROC curve increased with age in children aged 3 - 6 years. Conclusion This cross-sectional study found that the hyperopia reserve in children of different ages can be estimated using the hyperopia reserve equation. Additionally, the AL/CR ratio can serve as an effective index for detecting hyperopia reserve insufficiency, with an optimal ROC curve cut-off point of >= 2.91 in preschool children aged 3 - 6 years, and the critical value increasing with age.