title: Astigmatism in Chinese preschool children: prevalence, change, and effect on refractive development.
abstract: OBJECTIVE
  To study the prevalence, type, and progression of astigmatism in Chinese preschool children, and its effect on refractive development.
  
  
  METHODS
  A cross sectional study of preschool children was carried out in two randomly selected kindergartens. A cohort study was performed on a subset of children, five years after initial examination. Refractive error (measured by cycloplegic autorefraction) and axial ocular dimensions (measured by ultrasonography) were the main study outcomes.
  
  
  RESULTS
  522 children participated in the study; the mean age was 55.7 months (SD 10.9; range 27 to 77). Mean cylinder reading was -0.65 D (SD 0.58; range 0.00 to -4.75), and with the rule astigmatism was predominant (53%). In the 108 children studied longitudinally, the mean cylinder reading reduced from -0.62 D to -0.50 D (p = 0.019). The presence of astigmatism in initial examination predisposed the eyes towards greater myopisation (p<0.001). In addition, children with increased astigmatism had greater myopic progression (p<0.001) and axial length growth (p = 0.002).
  
  
  CONCLUSIONS
  This study reports a high prevalence of astigmatism in Chinese preschool children. The presence of astigmatism, and particularly with increasing astigmatism, appears to predispose the children to progressive myopia. Further studies are warranted.
authors.affiliation: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, 3/F, University Eye Center, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong. dennislam@cuhk.edu.hk
authors.forename: D S P
authors.initials: DS
authors.lastname: Fan
authors.forename: S K
authors.initials: SK
authors.lastname: Rao
authors.forename: E Y Y
authors.initials: EY
authors.lastname: Cheung
authors.forename: M
authors.initials: M
authors.lastname: Islam
authors.forename: S
authors.initials: S
authors.lastname: Chew
authors.forename: D S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000704:Analysis of Variance; D001251:Astigmatism / Q000150:complications / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009216:Myopia / Q000453:epidemiology* / Q000209:etiology; D015995:Prevalence