title: Effect of glaucomatous damage on repeatability of confocal scanning laser ophthalmoscope, scanning laser polarimetry, and optical coherence tomography.
abstract: OBJECTIVE
  To determine and compare the effect of the severity of glaucomatous damage on the repeatability of retinal nerve fiber layer (RNFL) thickness with GDx-VCC (variable corneal compensation) and StratusOCT (optical coherence tomography; both produced by Carl Zeiss Meditec, Inc., Dublin, CA), and optic nerve head (ONH) topography with HRT-II (retinal tomograph; Heidelberg Engineering GmbH, Heidelberg, Germany) and StratusOCT.
  
  
  METHODS
  With each of these techniques, two measurements were obtained from 41 eyes of 41 control subjects and 98 glaucomatous eyes (37 patients with early, 29 with moderate, and 32 with severe field loss). To evaluate test-retest variability at each stage, limits of agreement (Bland-Altman plots) and repeatability coefficients (RCs) were obtained from pairs of measurements. Comparisons of within-subject variances were used to compare repeatability of GDx-VCC versus StratusOCT for global RNFL and HRT-II versus StratusOCT for global ONH topography. Effects from age, visual acuity, and lens status were also included in the analysis as covariates.
  
  
  RESULTS
  Test-retest variability of RNFL using GDx-VCC and StratusOCT were consistent through all stages of disease severity. Repeatability results of GDx-VCC were better than those of StratusOCT, except in severe cases. Test-retest variability of ONH topography using HRT-II and StratusOCT increased with increasing disease severity for rim area, cup area, and cup-to-disc (C/D) area ratio. In contrast, vertical C/D ratio from HRT-II, and horizontal C/D ratio from StratusOCT showed stable test-retest variability through all stages. Regardless of disease severity, repeatability results of HRT-II were better than those of StratusOCT.
  
  
  CONCLUSIONS
  GDx-VCC and HRT-II showed better repeatability than StratusOCT. Although test-retest variability increased with disease severity for rim area, the variability for vertical C/D ratio (HRTII) and global RNFL (GDx-VCC) was stable across disease severity. These parameters, rather than rim area, may be more useful in detection of progression in patients with glaucoma who have more advanced field loss.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Julio E
authors.initials: JE
authors.lastname: DeLeón Ortega
authors.forename: Lisandro M
authors.initials: LM
authors.lastname: Sakata
authors.forename: Bobby
authors.initials: B
authors.lastname: Kakati
authors.forename: Gerald
authors.initials: G
authors.lastname: McGwin
authors.forename: Blythe E
authors.initials: BE
authors.lastname: Monheit
authors.forename: Stella N
authors.initials: SN
authors.lastname: Arthur
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Girkin
mesh_terms: D000328:Adult; D003952:Diagnostic Imaging / Q000592:standards*; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D007834:Lasers; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009887:Ophthalmoscopy; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests / Q000379:methods