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Bruno Lumbroso, Dafna Goldenberg, Florence Coscas, Joel Uzzan, Marco Rispoli, Anat Loewenstein, Gabriel J. Coscas; Choroid Thickness Measurement Comparison between RTVue with Tracking and Spectralis EDI. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2646.
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© ARVO (1962-2015); The Authors (2016-present)
FD-OCT devices vary in choroid image contrast, resolution of fine features, and the lateral and axial scaling factors for distance and thickness conversion. Choroid thickness measurement may be affected by the choice of device. This study compares thickness measurement between RTVue FD-OCT with tracking and Spectralis EDI.
This is an IRB approved international multi-center prospective study to evaluate choroid in normal, myopic, and AMD (dry or wet) eyes. Horizontal and vertical 30° B-Scan images were acquired through the center of the fovea with RTVue (Optovue, Fremont, CA) and Spectralis (Heidelberg Engineering, Germany). To enhance choroid image contrast, the Chorioretinal Mode for RTVue and EDI for Spectralis were employed. Tracking was enabled for both devices with 50 repetitions. Manual measurement of a subset of the study eyes were performed by two graders, one for each system, following choroid boundary selection rule in the order of suprachoroid space, lamina fusca, and outer limit of choroid vessels. Measurements were obtained from fovea, and 1500 µm from fovea in temporal, nasal, inferior, and superior respectively.
The subset consisted of 18 eyes (of 18 subjects), 9 normal and myopic eyes and 9 AMD eyes. There was good agreement in thickness measurement between RTVue and EDI for all 5 test locations with mean difference from 8.5 to 11.6 µm, standard deviation of difference from 6.9 to 15 µm, and occasionally, difference exceeding 30 µm (up to 39 µm) was observed. The difference between the two devices is small overall, considering the inherent variation of manual measurement method. Examination of extreme cases revealed some difference in contrast of suprachoroid space (Fig. A) and RPE edge (Fig. B) which may have affected grader judgment of the boundary, and transversal shift in peripheral test locations in occasional myopic eyes (Fig. C), possibly due to distance scaling.
There was good agreement in choroid thickness measurement between RTVue and Spectralis overall. Difference (up to 39 µm) was observed occasionally in some test cases. Further investigation needed to fully understand the reason for the outliers.
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