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Paul A Edwards, ; Optovue RTVue Retinal Thickness Reproducibility and Conversion to Stratus Metrics in DME. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3375.
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© ARVO (1962-2015); The Authors (2016-present)
Newer optical coherence tomography (OCT) devices that incorporate spectral domain (SD) technology are replacing time domain instruments. This study was performed to calculate measurement variability and relationships between retinal thickness (RT) measurements obtained on different instruments. These data are critical for proper use of RT measurements in clinical trials and clinical settings
A cross-sectional observational study was performed on diabetics with at least one eye having center-involved diabetic macular edema, defined as Stratus central subfield thickness (CST) >250 μm, by centers in DRCR.net. We evaluated the reproducibility of RT measurements from OCT images obtained with Zeiss Stratus and Optovue RTVue and formulated equations to convert RT measurements from RTVue to “equivalent” Stratus values. Each study eye underwent two replicate Stratus scans followed by two replicate RTVue scans centered on the fovea.
The Bland-Altman coefficient of repeatability for relative change in CST was not significantly different on Stratus and RTVue scans (10% and 16%, respectively). Replicate Stratus CST was within 10% of the initial Stratus CST 93% of the time; the CST conversion equation predicted a Stratus value calculated from the observed RTVue value within 10% of the observed Stratus thickness 91% of the time. The Bland-Altman limits of agreement for relative change in CST between measurements observed on different machines (the degree of change that could be expected from measurement variability within and between instruments) was 23%, comparing predicted versus actual Stratus measurement.
Reproducibility of RT with RTVue appears similar to Stratus. Conversion equations to transform RTVue measurements to Stratus-equivalent values within 10% of the observed Stratus RT are feasible. The RTVue reproducibility and conversion results are consistent with previously reported results on other SD machines; i.e., CST changes beyond 10% when using the same machine or 20% when switching from Stratus to SD machines, after conversion to Stratus equivalents, are likely due to a true change in RT beyond measurement error.
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