title: Sensitivity and specificity of a visual acuity screening protocol performed with the Lea Symbols 15-line folding distance chart in preschool children.
abstract: OBJECTIVE
  The aim of this study was to assess the feasibility of a visual acuity (VA) test using the Lea Symbols 15-line folding distance chart and its diagnostic validity in detecting VA deficiency in preschool children.
  
  
  METHODS
  A group of 149 children aged 38-54 months underwent VA examination performed with the Lea 15-line folding optotype at a distance of 3 metres, according to a test protocol described in the Methods section. After the VA test, a complete ophthalmological examination, including cycloplegic retinoscopy, a cover test and examination of the anterior and posterior segments, was performed on each child in order to detect any VA-threatening ocular abnormality. The Lea Symbols test's sensitivity, specificity, positive and negative likelihood ratios (LR +, LR -) and the receiver operating characteristic (ROC) curve were calculated by means of standard procedures using each VA level of the chart from 0.1 to 1 (1-0 logMAR) as a cut-off point.
  
  
  RESULTS
  The Lea Symbols test could be successfully used in 95.9% of the population. The most useful cut-off points for screening preschool children were found to be 0.8 (LR + 5.73, LR - 0.05) or 0.63 (LR + 11.7, LR - 0.23).
  
  
  CONCLUSIONS
  The Lea Symbols test proved to be clinically useful in detecting VA deficiency in preschool children. The choice between the two best performing cut-off levels should be made according to the expected cost-effectiveness of the screening programme.
authors.affiliation: Policlinico di Monza Hospital, Ophthalmology Clinic, University of Milano-Bicocca, Milan, Italy. francyhoney@libero.it
authors.forename: Francesca
authors.initials: F
authors.lastname: Bertuzzi
authors.forename: Jelka Gabriella
authors.initials: JG
authors.lastname: Orsoni
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Porta
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Paliaga
authors.forename: Stefano
authors.initials: S
authors.lastname: Miglior
mesh_terms: D002675:Child, Preschool; D005189:False Positive Reactions; D006801:Humans; D011237:Predictive Value of Tests; D012372:ROC Curve; D042262:Retinoscopy; D012680:Sensitivity and Specificity; D014786:Vision Disorders / Q000175:diagnosis*; D014787:Vision Tests / Q000295:instrumentation*; D014792:Visual Acuity