title: Comparison of retinal nerve fiber layer thickness measurement bias and imprecision across three spectral-domain optical coherence tomography devices.
abstract: OBJECTIVE
  We compared retinal nerve fiber layer (RNFL) bias and imprecision among three spectral-domain optical coherence tomographs (SD-OCT).
  
  
  METHODS
  A total of 152 eyes of 83 subjects (96 healthy and 56 glaucomatous eyes) underwent peripapillary RNFL imaging using at least 2 of the following 3 SD-OCT devices on the same day: Cirrus HD-OCT (optic nerve head [ONH]) cube 200 × 200 protocol), RTVue-100 (ONH protocol [12 radial lines and 13 concentric circles]), and 3D OCT-1000 (3D Scan 256 × 256 protocol). Calibration equations, bias and imprecision of RNFL measurements were calculated using structural equation models.
  
  
  RESULTS
  The calibration equations for healthy and glaucoma RNFL thickness measurements among the 3 devices were: Cirrus = 2.136 + 0.831*RTVue; Cirrus = -15.521 + 1.056*3D OCT-1000; RTVue = -21.257 + 1.271*3D OCT-1000. Using Cirrus bias as an arbitrary reference, RTVue bias was 1.20 (95% CI 1.09-1.32, P < 0.05) times larger and 3D OCT-1000 was 0.95 (0.87-1.03, P > 0.05) times smaller. Relative to 3D OCT-1000, the RTVue bias was 1.27 (1.13-1.42, P < 0.05). RTVue imprecision (healthy eyes 7.83, 95% CI 6.43-9.58; glaucoma cases 5.71, 4.19-7.64) was statistically significantly higher than both Cirrus (healthy eyes 3.23, 2.11-4.31; glaucoma cases 3.53, 0.69-5.24) and 3D OCT-1000 (healthy eyes 4.07, 3.11-5.35; glaucoma cases 5.33, 3.77-7.67) in healthy eyes. The imprecision also was significantly higher for RTVue measurements in healthy compared to glaucomatous eyes. None of the other comparisons was statistically significant.
  
  
  CONCLUSIONS
  RTVue-100 showed higher imprecision (or higher measurement variability) than Cirrus HD-OCT and 3D OCT-1000 RNFL measurements. Three-dimensional cube scanning with post-hoc data sampling may be a factor reducing imprecision.
authors.affiliation: Department of Ophthalmology, UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Buchser
authors.forename: Gadi
authors.initials: G
authors.lastname: Wollstein
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bilonick
authors.forename: Yun
authors.initials: Y
authors.lastname: Ling
authors.forename: Lindsey S
authors.initials: LS
authors.lastname: Folio
authors.forename: Larry
authors.initials: L
authors.lastname: Kagemann
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Noecker
authors.forename: Eiyass
authors.initials: E
authors.lastname: Albeiruti
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
mesh_terms: D000368:Aged; D005260:Female; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000295:instrumentation*