Longitudinal change in central corneal thickness among primary schoolchildren

To investigate the longitudinal changes in corneal thickness and its contributing factors in primary schoolchildren.

This study is a part of the Shahroud Schoolchildren Eye Cohort Study, conducted longitudinally in two phases; in 2015 and then in 2018. Participants were tested for uncorrected visual acuity, best-corrected visual acuity, cycloplegic refraction, biometry, and Scheimpflug corneal imaging.

After applying the exclusion criteria, 8782 eyes from 4432 participants were analysed. Of these, 2309 (52.1%) were male. Average three-year changes in central corneal thickness (CCT) and corneal apex thickness were -0.58 (95% CI: -0.94 to -0.22) and -0.59 (95% CI: -0.95 to -0.23) microns, respectively. There was an increase of 8.63 (95% CI: 8.1 to 9.17) microns in the superior corneal thickness after three years while the inferior corneal thickness decreased by an average of -5.75 (95% CI: -6.3 to -5.2) microns. The multiple generalized estimating equation (GEE) model showed that the three-year changes in the CCT were lower in rural than in urban students (β = -1.71; p < 0.001). Moreover, the baseline CCT (β = -0.04; p < 0.001), anterior chamber depth (β = -1.6; p = 0.003), and corneal diameter (β = -1.18; p < 0.001) had a significant inverse association while the body mass index (β = 0.12; p = 0.002) and axial length (β = 0.84; p < 0.001) had a significant direct association with the 3-year changes in CCT. After three years, CCT decreased by advancing age in boys, while remaining almost constant in girls.

The 3-year change in CCT was clinically negligible and could indicate its stability in schoolchildren. However, CCT thinning was more remarkable in urban students.