Agreement between spectral-domain and time-domain OCT for measuring RNFL thickness
- Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, California, USA
- Dr L M Zangwill, Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA, 9500 Gilman Drive #0946, La Jolla, CA 92093-0946, USA;
- Accepted 28 December 2008
- Published Online First 19 March 2009
Background/aims: 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 (R2 = 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 µm average RNFL thickness, 95% limits of agreement were −13.1 to 0.9 for healthy eyes and −16.2 to −0.3 µm 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.
Competing interests: Carl Zeiss Meditec: FAM (F, R), PAS (F), RNW (F,C), LMZ (F). Haag-Streit: PAS (F). Heidelberg Engineering: FAM (F), RNW (F), LMZ (F). Lace Elettronica: CB (F). Optovue: LMZ (F). Pfizer: CB (F). Reichert Instruments: FAM (R). Welch-Allyn: PAS (F).
Funding: NIH EY011008, NIH EY008208 and participant incentive grants in the form of glaucoma medication at no cost from Alcon Laboratories, Allergan, Pfizer and SANTEN.
Ethics approval: Ethics approval was provided by University of California San Diego Institutional Review Board.
Patient consent: Obtained.