title: Comparison of anterior and posterior topographic analysis between 3 imaging systems.
abstract: OBJECTIVE
  To evaluate and compare (anterior and posterior) corneal parameters obtained by use of 3 corneal topography devices.
  
  
  METHODS
  Tertiary referral eye center, Singapore.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Corneal measurements were obtained from 30 normal eyes and 40 eyes after Descemet-stripping automated endothelial keratoplasty (DSAEK) with use of the spectral-domain AS-OCT device, Scheimpflug device, and time-domain AS-OCT device. The posterior area analyzed, anterior and posterior keratometric values, keratometric power, and pachymetry were compared.
  
  
  RESULTS
  The spectral-domain AS-OCT device was able to capture the highest posterior area analyzed (86.2% ± 6.7%) compared with the Scheimpflug device (56.8% ± 11.9%) and the time-domain AS-OCT device (68.8% ± 12.3%) (P < .001). Intra-class coefficients (ICC) indicated strong agreement between devices in anterior keratometry (ICCs between 0.9 to 1.0) in both normal and DSAEK eyes. Agreement was poor to moderate for normal eyes (ICCs between 0.6 to 0.9) but poor in DSAEK eyes (ICCs between 0.60 to 0.7). For corneal pachymetry, agreement was moderate to strong for normal eyes (ICCs between 0.8 to 1.0) but showed poor to moderate agreement in DSAEK eyes (ICCs between 0.5 to 0.8). Vector analysis plots for mean astigmatism values showed greater differences between devices in anterior values compared with posterior values in both groups.
  
  
  CONCLUSIONS
  Although the agreement between imaging systems was good for anterior corneal topography, posterior corneal topography had moderate agreement in normal eyes and poor agreement in eyes after endothelial keratoplasty.
authors.affiliation: From Singapore National Eye Centre (Mi, Tan, Ang, Mehta), Singapore, Singapore Eye Research Institute (Ang, Mehta), Singapore, Duke-NUS Graduate Medical School (Mehta), Singapore.
authors.forename: Helen
authors.initials: H
authors.lastname: Mi
authors.affiliation: From Singapore National Eye Centre (Mi, Tan, Ang, Mehta), Singapore, Singapore Eye Research Institute (Ang, Mehta), Singapore, Duke-NUS Graduate Medical School (Mehta), Singapore.
authors.forename: Nathan
authors.initials: N
authors.lastname: Tan
authors.affiliation: From Singapore National Eye Centre (Mi, Tan, Ang, Mehta), Singapore, Singapore Eye Research Institute (Ang, Mehta), Singapore, Duke-NUS Graduate Medical School (Mehta), Singapore.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ang
authors.affiliation: From Singapore National Eye Centre (Mi, Tan, Ang, Mehta), Singapore, Singapore Eye Research Institute (Ang, Mehta), Singapore, Duke-NUS Graduate Medical School (Mehta), Singapore.
authors.forename: Hla M
authors.initials: HM
authors.lastname: Htoon
authors.affiliation: From Singapore National Eye Centre (Mi, Tan, Ang, Mehta), Singapore, Singapore Eye Research Institute (Ang, Mehta), Singapore, Duke-NUS Graduate Medical School (Mehta), Singapore.
authors.forename: Jodhbir S
authors.initials: JS
authors.lastname: Mehta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000175:diagnosis* / Q000503:physiopathology; D063171:Corneal Pachymetry; D019781:Corneal Topography / Q000295:instrumentation*; D057111:Descemet Stripping Endothelial Keratoplasty; D004728:Endothelium, Corneal / Q000473:pathology*; D019573:Epithelium, Corneal / Q000473:pathology*; D005260:Female; D005642:Fuchs' Endothelial Dystrophy / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012017:Referral and Consultation; D015203:Reproducibility of Results; D062606:Tertiary Care Centers; D041623:Tomography, Optical Coherence