title: Risk factors for incident myopia in Australian schoolchildren: the Sydney adolescent vascular and eye study.
abstract: OBJECTIVE
  To examine the risk factors for incident myopia in Australian schoolchildren.
  
  
  METHODS
  Population-based, longitudinal cohort study.
  
  
  METHODS
  The Sydney Adolescent Vascular and Eye Study (SAVES) was a 5- to 6-year follow-up of the Sydney Myopia Study (SMS). At follow-up, 2103 children were reexamined: 892 (50.5%) from the younger cohort and 1211 (51.5%) from the older cohort. Of these, 863 in the younger cohort and 1196 in the older cohort had complete refraction data.
  
  
  METHODS
  Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1; Canon, Tokyo, Japan) was measured at baseline and follow-up. Myopia was defined as a spherical equivalent refraction of ≤-0.50 diopters (D). Children were classified as having incident myopia if they were nonmyopic at baseline and myopic in either eye at follow-up. A comprehensive questionnaire determined the amount of time children spent outdoors and doing near work per week at baseline, as well as ethnicity, parental myopia, and socioeconomic status.
  
  
  METHODS
  Incident myopia.
  
  
  RESULTS
  Children who became myopic spent less time outdoors compared with children who remained nonmyopic (younger cohort, 16.3 vs. 21.0 hours, respectively, P<0.0001; older cohort, 17.2 vs. 19.6 hours, respectively, P=0.001). Children who became myopic performed significantly more near work (19.4 vs. 17.6 hours; P=0.02) in the younger cohort, but not in the older cohort (P=0.06). Children with 1 or 2 parents who were myopic had greater odds of incident myopia (1 parent: odds ratio [OR], 3.2, 95% confidence interval [CI], 1.9-5.2; both parents: OR, 3.3, 95% CI, 1.6-6.8) in the younger but not the older cohort. Children of East Asian ethnicity had a higher incidence of myopia compared with children of European Caucasian ethnicity (both P<0.0001) and spent less time outdoors (both P<0.0001). A less hyperopic refraction at baseline was the most significant predictor of incident myopia. The addition of time outdoors, near work, parental myopia, and ethnicity to the model significantly improved the predictive power (P<0.0001) in the younger cohort but had little effect in the older cohort.
  
  
  CONCLUSIONS
  Time spent outdoors was negatively associated with incident myopia in both age cohorts. Near work and parental myopia were additional significant risk factors for myopia only in the younger cohort.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia.
authors.forename: Amanda N
authors.initials: AN
authors.lastname: French
authors.forename: Ian G
authors.initials: IG
authors.lastname: Morgan
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Rose
mesh_terms: D001315:Australia / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007899:Leisure Activities; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D009216:Myopia / Q000453:epidemiology*; D012307:Risk Factors; D011795:Surveys and Questionnaires