Corneal Asphericity Variations in Korean Myopic Children

Purpose: Corneal asphericity (Q-value) represents the difference in curvature from center to periphery of the cornea. This study evaluated horizontal and vertical asymmetry in corneal asphericity in myopic children and its relationship with various ocular parameters.Methods: This retrospective study included 47 eyes in 24 myopic Korean children. Corneal parameters, such as corneal asphericity and thickness, apical radius of curvature, and high order aberrations including total root mean square (RMS), spherical aberration, coma, and trefoil were analyzed by Pentacam. Axial lengths (ALs) and anterior chamber depths (ACDs) were measured by IOL master. From these values, characteristics of corneal asphericity differences between nasal-temporal and superior-inferior quadrants in myopic children and their relationship with other ocular parameters were evaluated.Results: The mean Q-value (8 mm) was -0.34 ± 0.10, representing a prolate corneal shape. The mean superior-inferior Q-value differences (8 mm) was 0.23 ± 0.17, which was greater than the mean nasal-temporal Q-value differences (8 mm) measured as 0.15 ± 0.13. The mean Q-value (8 mm) was not significantly related to AL or ACD, and Q-values in each quadrant (8 mm) also showed no significant relationship with corneal thickness in each corresponding quadrant. The nasal-temporal Q-value differences (8 mm) had a positive relationship with total RMS (p = 0.001) and a negative relationship with oblique trefoil (p = 0.045) and spherical aberration (p = 0.007). The superior-inferior Q-value differences (8 mm) showed a negative relationship with vertical trefoil (p = 0.003).Conclusions: The results of the study showed a variation of nasal-temporal and superior-inferior Q-value differences, and the relationship between corneal shape and other ocular dimensions in myopic Korean children. Further study with large data set is merited to ascertain the epidemiologic data of Asian ethnicity.