title: Prevalence of myopia among Hong Kong Chinese schoolchildren: changes over two decades.
abstract: OBJECTIVE
  Studies have documented an increasing prevalence of myopia among urbanized Asian countries over recent decades. In the early 1990s, the reported prevalence rate was 25% and 64% for 6 and 12 year old children respectively. This cross-sectional study aims to determine the current prevalence of myopia amongst Hong Kong Chinese schoolchildren and whether there has been any increase over the last two decades.
  
  
  METHODS
  Data from 2651 children aged 6-12 (mean age: 8.92 ± 1.77, 53% boys) who participated in vision screening during 2005-2010 were analyzed. Visual parameters including visual acuity (in logMAR) and binocular status under the participants' habitual correction were assessed. Refractive errors were examined using non-cycloplegic auto-refraction and axial lengths were measured by partial coherence interferometry.
  
  
  RESULTS
  The mean spherical equivalent refraction for this population was -1.02 ± 1.70D, ranging from +4.75 to -10.00D. Prevalence of myopia (more than -0.50D) was 18.3% for the 6-year-old group and 61.5% for the 12-year-old group. Average myopia magnitude was -0.06 ± 1.03D at age 6 and -1.67 ± 1.99D at age 12. Prevalence of high myopia of more than -6.00D was 1.8%, with an increase from 0.7% at the age of 6 to 3.8% at the age of 12.
  
  
  CONCLUSIONS
  The prevalence of myopia among the Chinese schoolchildren population in Hong Kong as observed in this cross-sectional study are similar to our previously reported findings from almost two decades ago. There is no evidence that prevalence of myopia is increasing with time over the last two decades. However, the prevalence and degree of myopia in Chinese children is high as compared with other ethnic groups such as those reported among Caucasians.
authors.affiliation: Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Hong Kong. carly.lam@polyu.edu.hk
authors.forename: Carly Siu-Yin
authors.initials: CS
authors.lastname: Lam
authors.forename: Chin-Hang
authors.initials: CH
authors.lastname: Lam
authors.forename: Sam Chi-Kwan
authors.initials: SC
authors.lastname: Cheng
authors.forename: Lily Yee-Lai
authors.initials: LY
authors.lastname: Chan
mesh_terms: D000367:Age Factors; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D009216:Myopia / Q000453:epidemiology*; D015995:Prevalence; D012030:Refractive Errors / Q000453:epidemiology; D012737:Sex Factors