title: Retinal nerve fiber layer thickness measurement comparability between time domain optical coherence tomography (OCT) and spectral domain OCT.
abstract: OBJECTIVE
  Time domain optical coherence tomography (TD-OCT) has been used commonly in clinical practice, producing a large inventory of circular scan data for retinal nerve fiber layer (RNFL) assessment. Spectral domain (SD)-OCT produces three-dimensional (3-D) data volumes. The purpose of this study was to create a robust technique that makes TD-OCT circular scan RNFL thickness measurements comparable with those from 3-D SD-OCT volumes.
  
  
  METHODS
  Eleven eyes of 11 healthy subjects and 7 eyes of 7 subjects with glaucoma were enrolled. Each eye was scanned with one centered and eight displaced TD-OCT scanning circles. One 3-D SD-OCT cube scan was obtained at the same visit. The matching location of the TD-OCT scanning circle was automatically detected within the corresponding 3-D SD-OCT scan. Algorithm performance was assessed by estimating the difference between the detected scanning circle location on 3-D SD-OCT volume and the TD-OCT circle location. Global and sectoral RNFL thickness measurement errors between the two devices were also compared.
  
  
  RESULTS
  The difference (95% confidence interval) in scanning circle center locations between TD- and SD-OCT was 2.3 (1.5-3.2) pixels (69.0 [45.0-96.0] microm on the retina) for healthy eyes and 3.1 (2.0-4.1) pixels (93.0 [60.0-123.0] microm on the retina) for glaucomatous eyes. The absolute RNFL thickness measurement difference was significantly smaller with the matched scanning circle.
  
  
  CONCLUSIONS
  Scan location matching may bridge the gap in RNFL thickness measurements between TD-OCT circular scan data and 3-D SD-OCT scan data, providing follow-up comparability across the two generations of OCTs.
authors.affiliation: UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, Swanson School of Engineering, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Jong S
authors.initials: JS
authors.lastname: Kim
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gabriele
authors.forename: Gadi
authors.initials: G
authors.lastname: Wollstein
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bilonick
authors.forename: Larry
authors.initials: L
authors.lastname: Kagemann
authors.forename: James G
authors.initials: JG
authors.lastname: Fujimoto
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
mesh_terms: D000328:Adult; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000379:methods*