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Adnan Rashid, Ursula Schmidt-Erfurth, Bianca Gerendas, Sebastian M Waldstein, Andreas Wahle, Christian Simader, Kyungmoo Lee, Kai Wang, Milan Sonka, Michael David Abramoff; Reproducibility of Total Retinal Thickness in 5 SD-OCT Scanners using Iowa Reference Algorithm. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4786.
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© ARVO (1962-2015); The Authors (2016-present)
A comparison of total retinal thickness (TRT) measurements is presented using the Iowa Reference Algorithm from 5 commercially available Spectral-Domain Optical Coherence tomography (SD-OCT) scanners.
Fovea-centered SD-OCT volumes from 11 subjects were obtained at the Vienna Reading Center, Austria: 4 normal, 1 atrophic AMD, 1 macular hole, 2 Stargardt’s, 3 atrophic CNV. Serial-imaging OCT scans (all 6×6×2 mm3) were obtained using: CirrusTM HD-OCT (Carl Zeiss Meditec, 512×128×1024 voxels), RTVue (Optovue, 513×101×640), RS 3000 (Nidek, 512×128×512), Heidelberg Spectralis® (Heidelberg Engineering, 512×49×496), Topcon (Topcon, 512×128×885). The Iowa Reference Algorithm, which routinely segments 10 retinal layers, measured TRT as the average of all the A-scan voxels between inner limiting membrane and Bruch’s membrane surfaces. The model of TRT measurement comparisons across the 5 SD-OCT devices is Χmi=αm+βm μi+εmi. Xmi is a measurement from a device expressing the true value μi with intercept αm and slope βm, with εmi having mean=0 and variance=1. This model is more general than limit of agreement analysis, as βm are not required to be the same and be equal to 1. Mendel test was used to investigate whether the 5 βm values are the same. Bland Altman plots are provided and 5 SD-OCT pairwise predictive equations expressed via method comparison, using “additivityTests” and “MethComp” from the R package.
Mendel test on the proposed model reveals that the five βm expressing that the differences among the TRT measurements are constant (p=0.992). Having established this, Table 1 details the ten predictive equations among 5 SD-OCT devices in a pair-wise manner. The scatter plots with predictive lines and upper/lower 95% confidence limits and Bland Altman plots are shown in Figure 1.
The achieved p-value of 0.992 with the proposed model for 5 SD-OCTs establishes the cross-scanner reproducibility of the Iowa Reference algorithm. TRT measurements are highly reproducible, thus facilitating multi-center studies with heterogeneous device utilization.
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