title: Near work, outdoor activity, and their association with refractive error.
abstract: OBJECTIVE
  To assess the relationship between near work, outdoor activity, and refractive error in schoolchildren in Beijing.
  
  
  METHODS
  The Beijing Myopia Progression Study is a hospital-based myopia study, in which 386 students from primary (aged 6 to 12 years) and secondary (aged 13 to 17 years) schools in the inner city of Beijing were enrolled. Cycloplegic refraction and a detailed questionnaire probing near, intermediate, and distance visual activities were completed.
  
  
  RESULTS
  Three hundred seventy (95.9%) of 386 students with complete cycloplegic autorefraction and myopia questionnaire data were enrolled in this study. Children with more near work time did not exhibit a significantly more myopic refraction in both the primary and secondary school levels after adjusting for the children's gender, outdoor activity time, and average parental refractive error. A significant association between outdoor activity time (in hours per day) and the children's spherical equivalent (in diopters) was found in the primary school students (β = 0.27, p = 0.03) but not in the secondary school students (β = 0.04, p = 0.70) after adjusting for similar confounders. The time spent on outdoor sports and outdoor leisure in the primary school students was also significantly associated with the children's spherical equivalent (β = 0.46, p = 0.04 and β = 0.31, p = 0.02, respectively). Primary school students with more time outdoors exhibited relatively less myopic refraction than their peers (ptrend = 0.0003), but this relation was not demonstrated in the secondary school children (ptrend = 0.53) after adjusting for similar confounders.
  
  
  CONCLUSIONS
  Higher levels of outdoor activity were associated with less myopic refraction in primary school students in the inner city of Beijing. Near work activity was not found to be associated with refraction at either school level.
authors.affiliation: *MD, PhD †BSOptom, PhD ‡MD §OD, PhD Clinical & Epidemiological Eye Research Center, The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China (ZL, GYM, YBL); College of Optometry, Midwestern University, Glendale, Arizona (BV); Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China (VJ, SSR); School of Environmental Science and Public Health, Wenzhou Medical University, Wenzhou, Zhejiang, China (GYM); Handan Eye Hospital, Handan, Hebei, China (TYG); Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Lab, Beijing, China (ZL, FHW, YBL); and Department of Biological and Vision Sciences, SUNY College of Optometry, New York, New York (KJC).
authors.forename: Zhong
authors.initials: Z
authors.lastname: Lin
authors.forename: Balamurali
authors.initials: B
authors.lastname: Vasudevan
authors.forename: Vishal
authors.initials: V
authors.lastname: Jhanji
authors.forename: Guang Yun
authors.initials: GY
authors.lastname: Mao
authors.forename: Tie Ying
authors.initials: TY
authors.lastname: Gao
authors.forename: Feng Hua
authors.initials: FH
authors.lastname: Wang
authors.forename: Shi Song
authors.initials: SS
authors.lastname: Rong
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ciuffreda
authors.forename: Yuan Bo
authors.initials: YB
authors.lastname: Liang
mesh_terms: D000293:Adolescent; D002648:Child; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D034201:Computers, Handheld; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008297:Male; D009216:Myopia / Q000453:epidemiology*; D011932:Reading; D012029:Refraction, Ocular / Q000502:physiology; D013177:Sports; D011795:Surveys and Questionnaires; D014792:Visual Acuity / Q000502:physiology; D014937:Work