title: Comparison of optic nerve head parameter measurements obtained by time-domain and spectral-domain optical coherence tomography.
abstract: OBJECTIVE
  To compare the measurements of the optic nerve head (ONH) parameters provided by time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT).
  
  
  METHODS
  Four ONH parameters were analyzed: optic disc area, rim area, cup-to-disc area ratio (CDR), and vertical cup-to-disc ratio (VCDR). Stratus OCT and Cirrus HD-OCT were used to obtain measurements by TD-OCT and SD-OCT, respectively. Stratus OCT measurements were collected before and after manual correction of the ONH edges.
  
  
  RESULTS
  Twenty healthy participants and 20 patients with glaucomatous eyes were enrolled. Although manual correction of Stratus OCT measurements reduced the differences compared with Cirrus HD-OCT, the latter measured a smaller mean disc area than Stratus OCT in healthy (2.02±0.31 vs. 2.18±0.29 mm2, P=0.0003) and glaucomatous eyes (1.92±0.35 vs. 2.19±0.38 mm2, P<0.0001). Cirrus HD-OCT measured a smaller rim area than Stratus OCT in healthy (1.31±0.30 vs. 1.56±0.32 mm2, P<0.0001) and glaucomatous eyes (0.80±0.25 vs. 0.97±0.36 mm2, P=0.0052), a higher CDR (0.55±0.11 vs. 0.49±0.11, P<0.0001) and VCDR in healthy eyes (0.55±0.11 vs. 0.49±0.11, P<0.0001), and a higher CDR in glaucomatous eyes (0.74±0.10 vs. 0.58±0.18, P<0.0001). No statistically significant differences were detected for VCDR in glaucomatous eyes. All measured values showed good correlation (r≥0.70). Large 95% limits of agreement between the 2 devices were found for most parameters.
  
  
  CONCLUSIONS
  ONH parameter measurements provided by TD-OCT and SD-OCT show significant differences and cannot be considered interchangeable.
authors.affiliation: GB Bietti Eye Foundation-IRCCS, Rome, Italy. giacomo.savini@alice.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.forename: Piero
authors.initials: P
authors.lastname: Barboni
authors.forename: Michele
authors.initials: M
authors.lastname: Carbonelli
authors.forename: Alessandra
authors.initials: A
authors.lastname: Sbreglia
authors.forename: Giulia
authors.initials: G
authors.lastname: Deluigi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Parisi
mesh_terms: D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D057066:Low Tension Glaucoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000295:instrumentation*; D014794:Visual Fields