title: Effectiveness of screening preschool children for amblyopia: a systematic review.
abstract: BACKGROUND
  Amblyopia and amblyogenic factors like strabismus and refractive errors are the most common vision disorders in children. Although different studies suggest that preschool vision screening is associated with a reduced prevalence rate of amblyopia, the value of these programmes is the subject of a continuing scientific and health policy discussion. Therefore, this systematic review focuses on the question of whether screening for amblyopia in children up to the age of six years leads to better vision outcomes.
  
  
  METHODS
  Ten bibliographic databases were searched for randomised controlled trials, non-randomised controlled trials and cohort studies with no limitations to a specific year of publication and language. The searches were supplemented by handsearching the bibliographies of included studies and reviews to identify articles not captured through our main search strategy.
  
  
  RESULTS
  Five studies met the inclusion criteria. Of these, three studies suggested that screening is associated with an absolute reduction in the prevalence of amblyopia between 0.9% and 1.6% (relative reduction: between 45% and 62%). However, the studies showed weaknesses, limiting the validity and reliability of their findings. The main limitation was that studies with significant results considered only a proportion of the originally recruited children in their analysis. On the other hand, retrospective sample size calculation indicated that the power based on the cohort size was not sufficient to detect small changes between the groups. Outcome parameters such as quality of life or adverse effects of screening have not been adequately investigated in the literature currently available.
  
  
  CONCLUSIONS
  Population based preschool vision screening programmes cannot be sufficiently assessed by the literature currently available. However, it is most likely that the present systematic review contains the most detailed description of the main limitations in current available literature evaluating these programmes. Therefore, future research work should be guided by the findings of this publication.
authors.affiliation: Department of Medical Biometry and Statistics (German Cochrane Center), Institute of Medical Biometry and Medical Informatics, University Medical Center, Freiburg, Germany. schmucker@cochrane.de
authors.forename: Christine
authors.initials: C
authors.lastname: Schmucker
authors.forename: Robert
authors.initials: R
authors.lastname: Grosselfinger
authors.forename: Rob
authors.initials: R
authors.lastname: Riemsma
authors.forename: Gerd
authors.initials: G
authors.lastname: Antes
authors.forename: Stefan
authors.initials: S
authors.lastname: Lange
authors.forename: Wolf
authors.initials: W
authors.lastname: Lagrèze
authors.forename: Jos
authors.initials: J
authors.lastname: Kleijnen
mesh_terms: D000550:Amblyopia / Q000175:diagnosis* / Q000517:prevention & control; D002675:Child, Preschool; D016021:Epidemiologic Studies; D006801:Humans; D017063:Outcome Assessment, Health Care; D015397:Program Evaluation; D015351:Vision Screening