title: Worldwide prevalence and risk factors for myopia.
abstract: BACKGROUND
  Myopia, the most common type of refractive error, is a complex trait including both genetic and environmental factors. Numerous studies have tried to elucidate the aetiology of myopia. However, the exact aetiology of myopia is still unclear.
  
  
  OBJECTIVE
  To summarize the worldwide patterns and trends for the prevalence of myopia and to evaluate the risk factors for myopia in population-based studies.
  
  
  RESULTS
  The prevalences of myopia vary across populations of different regions and ethnicities. In population-based studies on children, the prevalence of myopia has been reported to be higher in urban areas and Chinese ethnicity. The regional and racial difference is not so obvious in adult populations aged over 40 years. More time spent on near work, less time outdoors, higher educational level and parental history of myopia have been reported to increase the risk of myopia.
  
  
  CONCLUSIONS
  Environmental factors play a crucial role in myopia development. The effect of gene-environment interaction on the aetiology of myopia is still controversial with inconsistent findings in different studies. A relatively hyperopic periphery can stimulate compensating eye growth in the centre. Longitudinal cohort studies or randomized clinical trials of community-based health behaviour interventions should be conducted to further clarify the aetiology of myopia.
authors.affiliation: Department of Epidemiology and Public Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Chen-Wei
authors.initials: CW
authors.lastname: Pan
authors.forename: Dharani
authors.initials: D
authors.lastname: Ramamurthy
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
mesh_terms: D017677:Age Distribution; D000818:Animals; D004522:Educational Status; D014943:Global Health; D006801:Humans; D008019:Life Style; D008251:Macaca; D009216:Myopia / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D015995:Prevalence; D012307:Risk Factors; D014794:Visual Fields / Q000502:physiology