Background/aims: To evaluate Spectral-Domain (SD) OCT reproducibility and assess the agreement between SD-OCT and Time-Domain (TD) OCT 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 microns Average RNFL thickness, 95% limits of agreement were –13.1 to 0.9 for healthy eyes and –16.2 to –0.3 microns for patient eyes).
Conclusions: SD-OCT measurements were highly repeatable in healthy and patient eyes. Although agreement between instruments was good, TD-OCT provided thicker RNFL measurements than SD-OCT. Measurements with these instruments should not be considered interchangeable.
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