title: Standardized color-coded scales for anterior and posterior elevation maps of scanning slit corneal topography.
abstract: OBJECTIVE
  To find the most appropriate color-coded scales for the anterior and posterior elevation maps of scanning slit topography in the screening of abnormal corneas such as keratoconus.
  
  
  METHODS
  Retrospective case-control study.
  
  
  METHODS
  Eighty eyes of 40 normal subjects and 175 eyes of 95 patients with keratoconus.
  
  
  METHODS
  Anterior and posterior corneal elevations were assessed using Orbscan 2. Best-fit sphere maps were drawn with several color-coded scales: 2-, 5-, 10-, and 20-microm height per each color interval.
  
  
  METHODS
  The maps were judged to be abnormal when more than three colors (discriminant number) were found within the central 3-mm area. For each color-coded scale, sensitivity, specificity, positive predictive value, negative predictive value, and sensitivity + specificity were calculated. After determining the most appropriate color-coded scales for the anterior and posterior elevation maps, validity of the discriminant number was assessed. By varying the discriminant number from two to eight, receiver operator characteristic (ROC) curves were created using the sensitivity and specificity for each threshold number.
  
  
  RESULTS
  The highest sensitivity + specificity values and highly balanced predictive values were obtained with the 10- and 20-microm scales for the anterior and posterior elevation maps, respectively. The ROC curve analyses showed that the best discriminant color number is three, indicating that maps with four or more colors within the central 3-mm area are judged abnormal in screening.
  
  
  CONCLUSIONS
  The 10- and 20-microm interval color scales are most appropriate for the anterior and posterior elevation maps of the scanning slit topography, respectively.
authors.affiliation: Department of Ophthalmology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Tanabe
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Oshika
authors.forename: Atsuo
authors.initials: A
authors.lastname: Tomidokoro
authors.forename: Shiro
authors.initials: S
authors.lastname: Amano
authors.forename: Sumiyoshi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Teruhito
authors.initials: T
authors.lastname: Kuroda
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Maeda
authors.forename: Tadatoshi
authors.initials: T
authors.lastname: Tokunaga
authors.forename: Kazunori
authors.initials: K
authors.lastname: Miyata
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D016022:Case-Control Studies; D002648:Child; D003116:Color; D019781:Corneal Topography / Q000379:methods*; D016002:Discriminant Analysis; D004728:Endothelium, Corneal / Q000473:pathology*; D019573:Epithelium, Corneal / Q000473:pathology*; D005189:False Positive Reactions; D006801:Humans; D007640:Keratoconus / Q000473:pathology*; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity