title: Corneal biomechanics, refractive error, and axial length in Chinese primary school children.
abstract: OBJECTIVE
  Low corneal hysteresis is associated with longer axial length in Chinese secondary school children. The authors sought to explore this association in primary school children.
  
  
  METHODS
  LogMAR presenting visual acuity, cycloplegic refractive error, ocular biometry, central corneal thickness (CCT), and corneal hysteresis (CH) was assessed for children in grades 1 to 3 at an academically competitive urban school in Shantou, China.
  
  
  RESULTS
  Among 872 eligible children (mean age, 8.6 ± 2.1 years), 651 (74.7%) completed the examination. Among 1299 examined eyes, 111 (8.5%) had uncorrected vision ≤6/12. Mean spherical equivalent refractive error for all eyes was +0.26 ± 1.41 D, and axial length (AL) was 22.7 ± 0.90 mm. CH for the lowest (mean AL, 21.7 ± 0.39 mm), two middle (mean AL, 22.4 ± 0.15 and 22.9 ± 0.15 mm), and highest quartiles (mean AL, 23.7 ± 0.74 mm) of AL were 10.6 ± 2.1 mm Hg, 10.4 ± 2.1 mm Hg, 10.3 ± 2.3 mm Hg, and 10.2 ± 2.3 mm Hg respectively (age- and gender-adjusted Pearson's correlation coefficient r = -0.052; P = 0.001). In generalized estimating equation models adjusting for age, gender, and CCT, lower CH was significantly associated with longer AL (P < 0.001) and more myopic refractive error (P = 0.001).
  
  
  CONCLUSIONS
  CH measurement is practical in young children because this is when myopia undergoes its most rapid progression. Prospective follow-up of this cohort at high risk for myopia is under way to determine whether low CH is predictive, or a consequence, of long AL.
authors.affiliation: Joint Shantou International Eye Center, Shantou, China.
authors.forename: Yuqiang
authors.initials: Y
authors.lastname: Huang
authors.forename: Chukai
authors.initials: C
authors.lastname: Huang
authors.forename: Liping
authors.initials: L
authors.lastname: Li
authors.forename: Kunliang
authors.initials: K
authors.lastname: Qiu
authors.forename: Weifen
authors.initials: W
authors.lastname: Gong
authors.forename: Zhenmao
authors.initials: Z
authors.lastname: Wang
authors.forename: Xuefen
authors.initials: X
authors.lastname: Wu
authors.forename: Yali
authors.initials: Y
authors.lastname: Du
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
authors.forename: Mingzhi
authors.initials: M
authors.lastname: Zhang
authors.forename: Nathan
authors.initials: N
authors.lastname: Congdon
mesh_terms: D044466:Asian People; D001696:Biomechanical Phenomena; D002648:Child; D002681:China / Q000453:epidemiology; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D012030:Refractive Errors / Q000208:ethnology / Q000503:physiopathology*; D012574:Schools; D014792:Visual Acuity