title: Comparing ophthalmoscopy, slide viewing, and semiautomated systems in optic disc morphometry.
abstract: OBJECTIVE
  To compare disc measurements obtained by indirect ophthalmoscopy, the Heidelberg Retina Tomograph (HRT), stereoscopic slide viewing (SSV) of color transparencies, and the Topcon ImageNet System (ImageNet).
  
  
  METHODS
  Population-based cross-sectional study.
  
  
  METHODS
  From the Rotterdam Study, 324 subjects (567 eyes) were nonselectively included. All underwent a full ophthalmologic examination in mydriasis. Vertical cup/disc ratios (VCDRs) were compared between all four methods and disc area (mm(2)), neural rim area (mm(2)), cup area (mm(2)), and cup volume (mm(3)) between HRT and ImageNet.
  
  
  RESULTS
  Mean VCDR for ophthalmoscopy was 0.25 (standard error [SE], 0.007), for HRT 0.42 (SE, 0.008), for SSV 0.39 (SE, 0.010), and for ImageNet 0.50 (SE, 0.006). The correlation for VCDR between ophthalmoscopy, the two devices, and SSV was 0.42, respectively 0.57; between ImageNet and HRT 0.75. The 97.5th percentiles of the VCDR for ophthalmoscopy, HRT, SSV, and ImageNet were 0.80, 0.73, 0.80, and 0.73, respectively; the 99.5th percentiles thus were 0.90, 0.79, 0.86, and 0.79. The mean disc area, rim area, cup area, and cup volume were 2.08, 1.63, 0.45 mm(2) and 0.09 mm(3) for HRT, and 2.39, 1.77, 0.61 mm(2) and 0.16 mm(3) for ImageNet, respectively. The corresponding correlations for these four parameters were 0.67, 0.42, 0.81, and 0.82.
  
  
  CONCLUSIONS
  Different techniques lead to considerable differences in disc morphometric values. ImageNet produced higher mean values compared with HRT and ophthalmoscopy. Ophthalmoscopy showed the lowest correlations and SSV the highest ones with the two semiautomated devices. Between ImageNet and HRT the correlation for all parameters was high except for the neural rim area.
authors.affiliation: Department of Epidemiology and Biostatistics, Erasmus University, Rotterdam, The Netherlands.
authors.forename: M Kamran
authors.initials: MK
authors.lastname: Ikram
authors.forename: Petra H
authors.initials: PH
authors.lastname: Borger
authors.forename: Jacqueline J M
authors.initials: JJ
authors.lastname: Assink
authors.forename: Jost B
authors.initials: JB
authors.lastname: Jonas
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Paulus T V M
authors.initials: PT
authors.lastname: de Jong
mesh_terms: D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods; D009898:Optic Disk / Q000033:anatomy & histology*; D010781:Photography / Q000379:methods; D015203:Reproducibility of Results; D014054:Tomography / Q000379:methods