title: Ability of the heidelberg retina tomograph to detect early glaucomatous visual field loss.
abstract: OBJECTIVE
  The Heidleberg Retina Tomograph provides rapid, reproducible measurements of optic disc topography as well as calculations of disc parameters. We used a stepwise discriminant analysis to determine which parameters were most useful in detecting individuals with early glaucomatous visual field loss.
  
  
  METHODS
  We studied one eye in each of 45 normal individuals and one eye in each of 46 individuals with early glaucomatous visual field loss. The appearance of the optic disc was not used for classification purposes so as not to bias the diagnostic determination obtained by the instrument. The data were analyzed using the reference plane of the software version 1.10 and using a method incorporating the height of the papillomacular bundle as reference level with and without age correction.
  
  
  RESULTS
  We obtained an 89% sensitivity and 78% specificity for the detection of early visual field loss using the standard reference level. The jackknife classification revealed lower sensitivity of 87% and an unchanged specificity of 78%. With the method incorporating the height of the papillomacular bundle as reference level, the sensitivity was 87% and the specificity was 84% for detecting early visual field loss. The jackknife classification revealed a sensitivity of 87% and a specificity of 82%. With the age correction, the sensitivity was 87%, specificity 84% with regular and jackknife classification. With the standard reference level, the important parameters were the third moment and the maximum depth, with the papillomacular bundle reference level volume above reference level added as important, and with age correction, height variation in contour replaced maximum depth in the analysis.
  
  
  CONCLUSIONS
  Three significant shape parameters of the optic disc can be used to detect early glaucomatous visual field loss.
authors.affiliation: *Departments of Ophthalmology and daggerMechanical Engineering, University of British Columbia, Vancouver, B.C., double dagger;Medical Engineering Group, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
authors.forename: F S
authors.initials: FS
authors.lastname: Mikelberg
authors.forename: C M
authors.initials: CM
authors.lastname: Parfitt
authors.forename: N V
authors.initials: NV
authors.lastname: Swindale
authors.forename: S L
authors.initials: SL
authors.lastname: Graham
authors.forename: S M
authors.initials: SM
authors.lastname: Drance
authors.forename: R
authors.initials: R
authors.lastname: Gosine