title: Estimating the magnitude of close-up work in school-age children: a comparison of questionnaire and diary instruments.
abstract: BACKGROUND
  Numerous scientists have noted a relationship between close-up work and myopia.
  
  
  METHODS
  A questionnaire and four 24-hour diaries were developed to estimate close-up work activity in a cohort study of close-up work and myopia progression in Singapore children. The number of hours per day that children engaged in each type of close-up work activity over a weekday and weekend during the school term, during the examination period, and in the vacation were estimated.
  
  
  RESULTS
  The children spent an average of 6.6 hours per day on total weighted average close-up work, of which 4.3 hours were spent on reading and writing. The intra-class correlation coefficient for the reproducibility of the questionnaire was 0.87 (95% CI 0.85-0.91). The intra-class correlation coefficient for total weighted close-up work was 0.50 (95% CI 0.34-0.66) when the questionnaire was compared with the four 24-hour diaries. The amount of close-up work activity increased with age.
  
  
  CONCLUSIONS
  A questionnaire for close-up work was developed and proven to be reproducible and comparable to four 24-hour diaries.
authors.affiliation: National University of Singapore, Department of Community, Occupational, and Family Medicine, Singapore, Singapore. cofsawsm@nus.edu.sg
authors.forename: S M
authors.initials: SM
authors.lastname: Saw
authors.forename: F J
authors.initials: FJ
authors.lastname: Nieto
authors.forename: J
authors.initials: J
authors.lastname: Katz
authors.forename: S J
authors.initials: SJ
authors.lastname: Chew
mesh_terms: D000203:Activities of Daily Living; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000453:epidemiology* / Q000209:etiology; D015995:Prevalence; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D012307:Risk Factors; D012846:Singapore / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014792:Visual Acuity; D014937:Work / Q000706:statistics & numerical data