title: Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial.
abstract: OBJECTIVE
  Myopia has reached epidemic levels in parts of East and Southeast Asia. However, there is no effective intervention to prevent the development of myopia.
  
  
  OBJECTIVE
  To assess the efficacy of increasing time spent outdoors at school in preventing incident myopia.
  
  
  METHODS
  Cluster randomized trial of children in grade 1 from 12 primary schools in Guangzhou, China, conducted between October 2010 and October 2013.
  
  
  METHODS
  For 6 intervention schools (n = 952 students), 1 additional 40-minute class of outdoor activities was added to each school day, and parents were encouraged to engage their children in outdoor activities after school hours, especially during weekends and holidays. Children and parents in the 6 control schools (n = 951 students) continued their usual pattern of activity.
  
  
  METHODS
  The primary outcome measure was the 3-year cumulative incidence rate of myopia (defined using the Refractive Error Study in Children spherical equivalent refractive error standard of ≤-0.5 diopters [D]) among the students without established myopia at baseline. Secondary outcome measures were changes in spherical equivalent refraction and axial length among all students, analyzed using mixed linear models and intention-to-treat principles. Data from the right eyes were used for the analysis.
  
  
  RESULTS
  There were 952 children in the intervention group and 951 in the control group with a mean (SD) age of 6.6 (0.34) years. The cumulative incidence rate of myopia was 30.4% in the intervention group (259 incident cases among 853 eligible participants) and 39.5% (287 incident cases among 726 eligible participants) in the control group (difference of -9.1% [95% CI, -14.1% to -4.1%]; P < .001). There was also a significant difference in the 3-year change in spherical equivalent refraction for the intervention group (-1.42 D) compared with the control group (-1.59 D) (difference of 0.17 D [95% CI, 0.01 to 0.33 D]; P = .04). Elongation of axial length was not significantly different between the intervention group (0.95 mm) and the control group (0.98 mm) (difference of -0.03 mm [95% CI, -0.07 to 0.003 mm]; P = .07).
  
  
  CONCLUSIONS
  Among 6-year-old children in Guangzhou, China, the addition of 40 minutes of outdoor activity at school compared with usual activity resulted in a reduced incidence rate of myopia over the next 3 years. Further studies are needed to assess long-term follow-up of these children and the generalizability of these findings.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00848900.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China2Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne.
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China3National Centre for Epidemiology and Population Health, Australian National University, Canberra.
authors.forename: Fan
authors.initials: F
authors.lastname: Xiang
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Yangfa
authors.initials: Y
authors.lastname: Zeng
authors.affiliation: Guangzhou Student's Health Care Institute of the Guangdong City Department of Education, Guangzhou, China.
authors.forename: Jincheng
authors.initials: J
authors.lastname: Mai
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Qianyun
authors.initials: Q
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Environmental Health Branch, NSW Department of Health, Sydney, Australia.
authors.forename: Wayne
authors.initials: W
authors.lastname: Smith
authors.affiliation: Discipline of Orthoptics, Faculty of Health Sciences, University of Sydney, Sydney, Australia7Discipline of Orthoptics, Graduate School of Health, University of Technology Sydney, Sydney, Australia.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Rose
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China8Research School of Biology, Australian National University, Canberra.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Morgan
mesh_terms: D002648:Child; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009216:Myopia / Q000453:epidemiology* / Q000517:prevention & control*; D011680:Pupil / Q000502:physiology; D011998:Recreation; D012029:Refraction, Ocular; D012574:Schools; D011795:Surveys and Questionnaires; D013997:Time Factors