title: Cornea biomechanical characteristics and their correlates with refractive error in Singaporean children.
abstract: OBJECTIVE
  To determine 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 cornea-compensated 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 distribution of the sexes was almost equal (138 boys, 50.9%), and most were Chinese (186 subjects, 68.6%). The mean (+/-SD) CH and CRF were 11.78 +/- 1.55 (range, 6.93-16.53) and 11.81 +/- 1.71 (range, 7.83-16.83) mm Hg. 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 (Pearson correlation coefficient [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, sex, 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 = -0.27 to -0.17]), CCT (beta = 0.03 [0.02-0.03]) and corneal curvature (beta = -1.13 [-2.08 to -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 to -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.
authors.affiliation: Singapore Eye Research Institute, Singapore.
authors.forename: Laurence
authors.initials: L
authors.lastname: Lim
authors.forename: Gus
authors.initials: G
authors.lastname: Gazzard
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: Allan
authors.initials: A
authors.lastname: Fong
authors.forename: Aachal
authors.initials: A
authors.lastname: Kotecha
authors.forename: Ee-Ling
authors.initials: EL
authors.lastname: Sim
authors.forename: Donald
authors.initials: D
authors.lastname: Tan
authors.forename: Louis
authors.initials: L
authors.lastname: Tong
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
mesh_terms: D000293:Adolescent; D001331:Automation; D001696:Biomechanical Phenomena; D001767:Blinking / Q000502:physiology; D002648:Child; D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology* / Q000503:physiopathology*; D003316:Corneal Diseases / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D009798:Ocular Hypertension / Q000503:physiopathology; D012030:Refractive Errors / Q000453:epidemiology / Q000503:physiopathology*; D012846:Singapore