title: The progression of refractive error in school-age children: Shunyi district, China.
abstract: OBJECTIVE
  To assess the progression of refractive error and the incidence of myopia in school-age children in the Shunyi District of Beijing, China.
  
  
  METHODS
  A longitudinal cohort study.
  
  
  METHODS
  A population-based sample of 4,662 children initially examined in 1998 at ages 5 to 13 years was reexamined between September and November, 2000. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression.
  
  
  RESULTS
  In 28.5 months, the average change in refractive error was -0.42 diopters (standard deviation, 0.68) in right eyes. Myopic shift of refractive error was associated with female sex, older age, and higher myopic or hyperopic refractive error at baseline. The average change in astigmatic error was essentially zero, with significant change in both directions more likely among those with higher baseline astigmatism. Findings were similar for left eyes. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of -0.50 diopters or more in either eye, among initial emmetropes and hyperopes was 14.1% (95% confidence interval [CI], 11.8%-16.5%) for male and 23.5% (95% CI, 20.8%-26.1%) for female subjects. Myopia incidence increased sixfold to sevenfold between baseline age 5 and 12, before decreasing at age 13, for both male and female subjects.
  
  
  CONCLUSIONS
  In the design of cost-effective programs for the periodic screening and treatment of uncorrected refractive error, children initially found to require refractive correction should be targeted for relatively frequent rescreening, as should girls and older children. Further study is required to better understand environmental and genetic risk factors for myopia development and progression.
authors.affiliation: Eye Research Center, Chinese Academy of Medical Sciences, Beijing, China.
authors.forename: Jialiang
authors.initials: J
authors.lastname: Zhao
authors.forename: Jin
authors.initials: J
authors.lastname: Mao
authors.forename: Rong
authors.initials: R
authors.lastname: Luo
authors.forename: Fengrong
authors.initials: F
authors.lastname: Li
authors.forename: Sergio R
authors.initials: SR
authors.lastname: Munoz
authors.forename: Leon B
authors.initials: LB
authors.lastname: Ellwein
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D009216:Myopia / Q000453:epidemiology* / Q000503:physiopathology* / Q000517:prevention & control; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors; D015351:Vision Screening