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Adnan Rashid, Ursula Schmidt-Erfurth, Bianca Gerendas, Sebastian Waldstein, Hrvoje Bogunovic, Andreas Wahle, Christian Simader, Kyungmoo Lee, Milan Sonka, Michael Abramoff; Total Retinal Thickness Using Iowa Reference Algorithm: Measurement Reproducibility in 5 SD-OCT Scanners. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5503.
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© ARVO (1962-2015); The Authors (2016-present)
A comparison of retinal thickness assessment obtained from the Iowa Reference Algorithm on commercially available spectral-domain (SD) optical coherence tomography (OCT) scanners from five different manufacturers.
Fovea-centered SD-OCT volumes from 11 eyes were obtained at the Vienna Reading Center: 4 normal eyes and 4 dry age-related macular degeneration, 1 lamellar macular hole and 2 Stargardt’s disease. Serial-imaging OCT scans (all 6×6×2 mm3) were obtained using: Cirrus HD-OCT (Carl Zeiss Meditec)(512×128×1024 voxels), RTVue (Optovue)(513×101×640), RS-3000 (Nidek)(512×128×512), Heidelberg Spectralis (Heidelberg Engr) (512×49×496) and Topcon-2000 (Topcon)(512×128×885). The Iowa Reference Algorithm, which routinely provides segmentation of 10 retinal layers, measured total retinal thickness (TRT), defined as averaged distances between the Inner Limiting Membrane and Bruch’s Membrane surfaces. The average of TRT obtained from all 5 scanners for each subject represented the patient-specific reference value of TRT. Scanner-specific bias was calculated as the mean signed difference between the reference standard and patient/scanner-specific TRT measurement and expressed in µm as mean ± stdv. TRT values from the 5 scanner segmentations were used to determine cross-scanner reproducibility of the Iowa Reference Algorithm.
In Fig. 1, scanner bias µbias(in µm) for Cirrus, Topcon, RTVue, RS3000 and Spectralis are -1.33, -1.50, 2.88, (high) 8.14 and (max) -8.19, with σbias of 1.64, 1.92, (min) 1.11, 1.81 and (max) 2.14, respectively. Fig. 2 shows that excellent cross-scanner reproducibility can be obtained by scanner-based bias correction - TRT measurements are tightly clustered around the same value for each subject.
Iowa Reference Algorithm allows comparisons of TRT across clinically-relevant SD-OCT scanners, i.e. Cirrus, Spectralis, Topcon, RTVue, and RS3000. The achieved variance of around 2 µm suggests - after correcting for the systematic scanner-specific measurement bias - that retinal thickness values obtained with the Iowa Reference Algorithm are highly comparable across scanners thus facilitating multi-center studies with heterogeneous device utilization.
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