Purpose:
To evaluate repeatability and agreement of RNFL thickness measurementsbetween Stratus OCT and RTVue SD OCT in normal and glaucomatoussubjects.
Methods:
22 subjects, of 60 planned, have been recruited (11 normal,11 glaucomatous; acuity 6/9; visual field MD (dB), normal =mean -0.29 (-2.14 to 0.91), glaucoma = mean -5.3 (-12.07 to-1.75)). Each was scanned in 2 sessions (within two months)by two expert operators with the RTVue Spectral Domain OCT (Optovue)and Stratus OCT (Carl Zeiss Meditec). RNFL was measured usingthe RNFL 3.45 (RTVue; average of four circular scans of 3.45mm diam. 1024 A scans) and the Fast RNFL thickness protocol(Stratus OCT; average of three circular scans of 3.4 mm diam.256 A scans). For the Stratus OCT the repeat function was usedin the second session. The scanning circle was centred at eachsession for the RTVue. Reproducibility and agreement was evaluatedby means of Bland Altman plots.
Results:
In all subjects image quality was better than SS = 7 for StratusOCT and better than SSI = 30 for RTVue. Subjects age (years):normal, mean 38 (range 24-47), glaucoma, mean 58 (range 26-80).RNFL thickness average both devices (microns): normal = mean105.7 (88 to 125), glaucoma = mean 82.4 (72 to 119).
Conclusions:
Preliminary results suggest repeatability is better in normalsubjects for both devices. The Stratus OCT showed narrower limitsof agreement in normal and glaucomatous subjects, possibly dueto the use of the repeat function or a difference in the segmentationalgorithm. Other scan patterns available on the RTVue may havesuperior reproducibility. Agreement between devices is betterin normal subjects. Limits of agreement are quite wide.
Keywords: nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)