title: Relation of childhood myopia progression rates to time of year.
abstract: BACKGROUND
  One potential method for assessment of the effect of near work on childhood myopia progression is to compare progression rates overtime spans that have differing near-point demands.
  
  
  METHODS
  Myopia progression rates were calculated for a 6-month period during the school year (called school rate in this article) and for a 6-month period that included the 3 months of summer vacation (called summer rate). Data used for analysis were right eye spherical equivalents from manifest subjective refractions of 27 children in a longitudinal study at Northeastern State University in Oklahoma, and 15 children in a longitudinal study at Indiana University. All subjects wore single-vision spectacle lenses.
  
  
  RESULTS
  The mean summer rate for the 42 subjects was -0.39 diopters per year (D/yr) (SD = 0.46). The mean school rate was -0.72 D/yr (SD = 0.57). The rates during the two periods were significantly different by two-tailed paired t-test (p = 0.006).
  
  
  CONCLUSIONS
  The differing amount of nearpoint activity during the school year and the summer is a potential explanation for the different rates of myopia progression during those two time periods.
authors.affiliation: School of Optometry, Indiana University, Bloomington 47405-3680, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Goss
authors.forename: B B
authors.initials: BB
authors.lastname: Rainey
mesh_terms: D002648:Child; D018450:Disease Progression; D006801:Humans; D008137:Longitudinal Studies; D009216:Myopia / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D012029:Refraction, Ocular; D012621:Seasons; D014792:Visual Acuity