Corneal Thickness Determination and Correlates in Singaporean Schoolchildren

Purpose: To determine the central cornea thickness (CCT) in Singaporean children and to examine the possible relationship between intraocular pressure (IOP) and other biometric factors and CCT.

Methods: This was a cross-sectional study. The subjects (N=652) were obtained from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). The subjects' ages ranged from 9 to 11 years. There were 485 Chinese, 92 Malayan, and 75 Asian Indian children. Measurement procedures included air-puff tonometry, noncontact slit lamp optical pachymetry, cycloplegic autorefraction, and autokeratometry.

Results: The mean CCT was 543.6 +/- 32.0 microm. Chinese children had thicker corneas than Malayan or Indian children (P=0.002). The boys had thicker corneas than girls (P=0.011), but the mean difference was only 6.4 microm. There was high correlation of CCT (r=0.98) and IOP (r=0.88) between right and left eyes. IOP was correlated with CCT (r=0.45, P <0.001). In a multiple linear regression model, each millimeter of mercury of IOP was associated with a CCT difference of 5.90 microm (95% confidence interval [CI], 4.98-6.82). The radius of corneal curvature correlated with CCT (r=0.19, P <0.001). The following parameters were not significantly (P >0.05) associated with CCT: age, family income, father's education, axial length, and spherical equivalent.

Conclusions: The mean CCT in Singaporean children aged 9 to 11 years was 543.6 microm and showed ethnic and gender variation. CCT affected measured IOP and correlated weakly with corneal curvature. Compared with data in adults, a change in CCT was associated with a greater difference in measured IOP.