Cornea Biomechanical Characteristics and their Correlates with Refractive Error in Singapore children

¹ Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore, 168751, Singapore
² Singapore Eye Research Institute, Singapore, Singapore; Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom; Singapore National Eye Centre, Singapore, Singapore
³ Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
⁴ Singapore Eye Research Institute, Singapore, Singapore; Singapore National Eye Centre, Singapore, Singapore
⁵ Glaucoma Research Unit, Moorfields Eye Hospital, London, United Kingdom
⁶ Singapore Eye Research Institute, Singapore, Singapore
⁷ Singapore National Eye Centre, Singapore, Singapore; Singapore Eye Research Institute, Singapore, Singapore
⁸ Singapore Eye Research Institute, Singapore, Singapore; Department of Community, Occupational, and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore

^* To whom correspondence should be addressed. E-mail: llimshen{at}gmail.com.

	Abstract

Purpose To determine the corneal biomechanical parameters measured with the Reichert Ocular Response Analyser (ORA) in Singaporean children, and to assess their possible correlations with refractive error and biometry. Methods This was a cross sectional study of 271 subjects from the Singapore Cohort Study of Risk Factors for Myopia (SCORM). Corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT) and intraocular pressure (IOPcc) were measured with the ORA. Spherical equivalent refraction was assessed with an autokeratorefractometer, and axial length by contact ultrasound A-scan biometry. Height, weight, and blood pressure were measured. Results The mean age of the study population was 13.97±0.89 years, the gender distribution was almost equal (138 males, 50.9%), and the majority were Chinese (186 subjects, 68.6%).The mean (± standard deviation) CH and CRF were 11.78 ± 1.55mmHg (range 6.93-16.53mmHg) and 11.81 ± 1.71mmHg (range 7.83-16.83mmHg). CH and CRF did not vary significantly with age (p = 0.24; 0.61), sex (p = 0.21; 0.08) or race (p = 0.23; 0.36). CH and CRF did not vary with myopia status (p = 0.79; 0.83), or axial length (r = -0.11 and -0.05, p = 0.08 and 0.40). Multivariate analyses were performed with CH, CRF or CCT as the dependent variable and age, gender, race, weight, IOPcc, CCT, SE refraction, and corneal curvature as covariates. CH was significantly associated with IOP (regression coefficients(beta)= -0.22 (95% confidence interval (CI)-0.27, -0.17)), CCT (beta= 0.03(0.02, 0.03)) and corneal curvature (beta = -1.13 (-2.08, -0.19)). CRF was significantly associated with IOP, CCT and corneal curvature. (beta= 0.08 (0.02, 0.14); 0.03(0.03, 0.04) and -1.39(-2.54, -0.23) respectively). The only factor that was predictive of decreased CCT was Malay or Indian race (p = 0.03 and <0.001), compared with Chinese. Conclusions The CH and CRF values in our study on Singaporean children are slightly higher than in adult studies. CH and CRF are not associated with refractive error or axial length. Flatter corneas are associated with lower CH and CRF readings.

Key Words: corneal biomechanics, refractive error, children-s vision