Three-year change in corneal asphericity in children at the age of emmetropisation

To determine the 3-year changes in anterior and posterior values of corneal asphericity (Q) in 6- to 12-year-old children.

The first and second phases of the study were conducted in 2015 and 2018, respectively. The target population in the first phase was 6- to 12-year-old students in Shahroud, Iran. Multistage cluster sampling was performed on urban students. Additionally, all rural students in Shahroud county were invited to participate. Corneal imaging and ocular biometry were performed using the Pentacam-HR and Allegro Biograph, respectively.

A total of 4961 right eyes were analysed in this report. The mean (95% confidence interval) anterior and posterior Q values for an 8-mm chord diameter were -0.38 ± 0.11 (-0.39 to -0.38) and -0.32 ± 0.12 (-0.33 to -0.32) in the first phase of the study, respectively. The mean 3-year changes in anterior and posterior Q values were 0.00 ± 0.08 (95% CI: 0.00-0.00) and -0.01 ± 0.06 (95% CI: -0.01 to -0.01), respectively. Based on a multiple regression model, advancing age (β = -0.002; [-0.003 to -0.001]), 3-year increase in mean keratometry (β = -0.04; [-0.06 to -0.02]), central corneal thickness (β = -0.001; [-0.001 to -0.000]), lens thickness (-0.05; [-0.11 to -0.003]) and anterior chamber depth (-0.09; [-0.15 to -0.03]) showed a statistically significant association with increased anterior Q prolation. Increased axial length was associated with a decrease in Q (β = 0.02; [0.004 to 0.03]). In addition, female gender (β = -0.004; [-0.007 to -0.001]) was significantly associated with a more prolate posterior Q value, while rural residence (β = 0.005; [0.002 to 0.009]) was significantly associated with a more oblate posterior Q value.

Three-year changes in anterior and posterior Q values were very small. The cornea tends to become more prolate with increasing age.