title: Agreement between spectral-domain and time-domain OCT for measuring RNFL thickness.
abstract: OBJECTIVE
  To evaluate spectral-domain (SD) optical coherence tomography (OCT) reproducibility and assess the agreement between SD-OCT and Time-Domain (TD) OCT retinal nerve fibre layer (RNFL) measurements.
  
  
  METHODS
  Three Cirrus-SD-OCT scans and one Stratus-TD-OCT scan were obtained from Diagnostic Innovations in Glaucoma Study (DIGS) healthy participants and glaucoma patients on the same day. Repeatability was evaluated using Sw (within-subject standard deviation), CV (coefficient of variation) and ICC (intraclass correlation coefficient). Agreement was assessed using correlation and Bland-Altman plots.
  
  
  RESULTS
  16 healthy participants (32 eyes) and 39 patients (78 eyes) were included. SD-OCT reproducibility was excellent in both groups. The CV and ICC for Average RNFL thickness were 1.5% and 0.96, respectively, in healthy eyes and 1.6% and 0.98, respectively, in patient eyes. Correlations between RNFL parameters were strong, particularly for average RNFL thickness (R(2) = 0.92 in patient eyes). Bland-Altman plots showed good agreement between instruments, with better agreement for average RNFL thickness than for sectoral RNFL parameters (for example, at 90 microm average RNFL thickness, 95% limits of agreement were -13.1 to 0.9 for healthy eyes and -16.2 to -0.3 microm for patient eyes).
  
  
  CONCLUSIONS
  SD-OCT measurements were highly repeatable in healthy and patient eyes. Although the agreement between instruments was good, TD-OCT provided thicker RNFL measurements than SD-OCT. Measurements with these instruments should not be considered interchangeable.
authors.affiliation: Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA.
authors.forename: G
authors.initials: G
authors.lastname: Vizzeri
authors.forename: R N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: A O
authors.initials: AO
authors.lastname: Gonzalez-Garcia
authors.forename: C
authors.initials: C
authors.lastname: Bowd
authors.forename: F A
authors.initials: FA
authors.lastname: Medeiros
authors.forename: P A
authors.initials: PA
authors.lastname: Sample
authors.forename: L M
authors.initials: LM
authors.lastname: Zangwill
mesh_terms: D000368:Aged; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology / Q000648:ultrastructure; D011446:Prospective Studies; D015203:Reproducibility of Results; D055351:Retinal Neurons / Q000166:cytology / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods*