title: Corneal hysteresis and axial length among Chinese secondary school children: the Xichang Pediatric Refractive Error Study (X-PRES) report no. 4.
abstract: OBJECTIVE
  To evaluate the association between corneal hysteresis and axial length/refractive error among rural Chinese secondary school children.
  
  
  METHODS
  Cross-sectional cohort study.
  
  
  METHODS
  Refractive error (cycloplegic auto-refraction with subjective refinement), central corneal thickness (CCT) and axial length (ultrasonic measurement), intraocular pressure (IOP), and corneal hysteresis (Reichert Ocular Response Analyzer) were measured on a rural school-based cohort of children.
  
  
  RESULTS
  Among 1,233 examined children, the mean age was 14.7 +/- 0.8 years and 699 (56.7%) were girls. The mean spherical equivalent (n = 1,232) was -2.2 +/- 1.6 diopters (D), axial length (n = 643) was 23.7 +/- 1.1 mm, corneal hysteresis (n = 1,153) was 10.7 +/- 1.6 mm Hg, IOP (n = 1,153) was 17.0 +/- 3.4 mm Hg, and CCT (n = 1,226) was 553 +/- 33 microns. In linear regression models, longer axial length was significantly (P < .001 for both) associated with lower corneal hysteresis and higher IOP. Hysteresis in this population was significantly (P < .001) lower than has previously been reported for normal White children (n = 42, 12.3 +/- 1.3 mm Hg), when adjusting for age and gender. This difference did not appear to depend on differences in axial length between the populations, as it persists when only Chinese children with normal uncorrected vision are included.
  
  
  CONCLUSIONS
  Prospective studies will be needed to determine if low hysteresis places eyes at risk for axial elongation secondary or if primary elongation results in lower hysteresis.
authors.affiliation: Joint Shantou International Eye Center of Shantou University, Shantou, PRC. sy@jsiec.org
authors.forename: Yue
authors.initials: Y
authors.lastname: Song
authors.forename: Nathan
authors.initials: N
authors.lastname: Congdon
authors.forename: Liping
authors.initials: L
authors.lastname: Li
authors.forename: Zhongxia
authors.initials: Z
authors.lastname: Zhou
authors.forename: Kai
authors.initials: K
authors.lastname: Choi
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
authors.forename: Chi Pui
authors.initials: CP
authors.lastname: Pang
authors.forename: Zhenling
authors.initials: Z
authors.lastname: Xie
authors.forename: Xueyu
authors.initials: X
authors.lastname: Liu
authors.forename: Abhishek
authors.initials: A
authors.lastname: Sharma
authors.forename: Weihong
authors.initials: W
authors.lastname: Chen
authors.forename: Mingzhi
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D044466:Asian People / Q000208:ethnology*; D002648:Child; D002681:China / Q000453:epidemiology; D003315:Cornea / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004547:Elastic Tissue / Q000503:physiopathology*; D004548:Elasticity; D005123:Eye / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D012030:Refractive Errors / Q000503:physiopathology*; D012424:Rural Population / Q000706:statistics & numerical data*