title: A comparison of structural measurements using 2 Stratus optical coherence tomography instruments.
abstract: OBJECTIVE
  To compare measures of peripapillary retinal nerve fiber layer (RNFL) thickness, optic disc topography, and central foveal thickness generated using 2 different Stratus optical coherence tomography (OCT) instruments.
  
  
  METHODS
  Ten normal subjects and 10 glaucoma subjects were included. One randomly selected eye per subject was scanned consecutively using a fast RNFL thickness protocol, fast macular thickness map, and fast optic disc protocol by 2 experienced operators on 2 instruments. The order of the machines and operators were randomized. The output power of each machine was measured using an optical power meter. For each OCT measurement 2 factor fixed effects analyses of variance were performed and a restricted maximum likelihood variance component analysis of the proportion of variance due to subject, operator, and machine was calculated.
  
  
  RESULTS
  Significant differences (P<or=0.003) between OCT instruments were observed in average, superior, and inferior RNFL thickness and central foveal thickness values among normal eyes; and average and superior RNFL thickness and cup/disc area ratio values among glaucomatous eyes. Overall, the intermachine variability (0.0% to 16.4%) was larger than the interoperator variability (0.0% to 2.4%) for all OCT measurements. In the glaucoma group the variability due to machine differences was 2.6 microm for the average RNFL thickness, 5.7 microm for the superior RNFL thickness, 0 microm for the inferior RNFL thickness, 0.03 microm for the cup/disc area ratio, 0.01 microm for the cup/disc vertical ratio, and 2.8 microm for the average foveal thickness.
  
  
  CONCLUSIONS
  Measurements of RNFL thickness, optic disc topography, and central foveal thickness significantly differ between OCT instruments.
authors: Department of Ophthalmology, University of Miami Miller School of Medicine, Bascom Palmer Eye Institute, Palm Beach Gardens, FL 33418, USA. msehi@med.miami.edu
authors: Mitra
authors: M
authors: Sehi
authors: Delia C
authors: DC
authors: Guaqueta
authors: William J
authors: WJ
authors: Feuer
authors: David S
authors: DS
authors: Greenfield
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005189:False Positive Reactions; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*