title: Observer experience and Cup:Disc ratio assessment.
abstract: BACKGROUND
  The validity of the Cup:Disc (C:D) ratio as a clinical measure depends on the level of agreement among observers. In this study, we investigated the effect of observer experience on interobserver and intraobserver agreement in C:D ratio estimation.
  
  
  METHODS
  Nine 3rd-year (Yr3) and nine 4th-year (Yr4) optometry students and nine optometrists (Opt), determined C:D ratios from 26 optic disc photographs viewed monoscopically and stereoscopically. Observer agreement was investigated using weighted kappa (Kw) analysis.
  
  
  RESULTS
  Interobserver agreement was higher (p < 0.01) among optometrists than among 4th-year students and higher (p < 0.01) among 4th-year than among 3rd-year students (mean Kw: Opt = 0.61; Yr4 = 0.51; Yr3 = 0.39). Stereoscopic estimates of C:D ratios were higher (p < 0.0001) than monoscopic estimates, and interobserver agreement was higher (p < 0.001) when evaluating the vertical rather than the horizontal C:D ratio. Intraobserver agreement (mean Kw: Opt = 0.67; Yr4 = 0.66; Yr3 = 0.62) did not vary significantly (p = 0.78) with experience.
  
  
  CONCLUSIONS
  The extent to which an observer reproducibly assesses the C:D ratio from optic disc photographs (intraobserver agreement) does not increase with experience. However, the agreement between different observers in assessing the C:D ratio (interobserver agreement) increases with experience.
authors.affiliation: Department of Optometry and Vision Science, The University of Auckland, New Zealand.
authors.forename: S
authors.initials: S
authors.lastname: Hanson
authors.forename: S K
authors.initials: SK
authors.lastname: Krishnan
authors.forename: J
authors.initials: J
authors.lastname: Phillips
mesh_terms: D002983:Clinical Competence / Q000592:standards*; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D015588:Observer Variation; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D009907:Optometry / Q000193:education / Q000592:standards; D010781:Photography; D015203:Reproducibility of Results; D013337:Students, Medical