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Moritz Niemeyer, Ken Marion, Srinivas R Sadda, Vikas Chopra; Evaluation and Comparison of Novel Anterior Chamber Angle Metrics Using Two Spectral Domain OCT Devices. Invest. Ophthalmol. Vis. Sci. 2014;55(13):940.
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© ARVO (1962-2015); The Authors (2016-present)
To compare novel Schwalbe’s line-based anterior chamber angle parameters obtained from two widely-available spectral domain optical coherence tomography (SD-OCT) instruments, and to evaluate the reproducibility of these metrics in normal and glaucomatous eyes.
Inferior irido-corneal angles of 95 eyes from 51 participants (30 Glaucoma and 21 normal) were scanned twice with the Optovue SD-OCT and Cirrus SD-OCT under controlled low luminance conditions. Novel metrics termed the Schwalbe’s line angle opening distance (SL-AOD) and SL trabecular-iris-space area (SL-TISA) were graded by masked certified graders at the Doheny Imaging Reading Center using customized Image J software. Inter-instrument agreement and inter-grader reproducibility of SL-AOD and SL-TISA measurements were evaluated by intra-class correlation coefficients (ICC), mean percent difference (MPD), and coefficient of variability (CV).
The mean SL-AOD for the total study cohort was 587 µm+/-247 µm (range 142-1121µm) for the Optovue and 596 µm+/-278 µm (122-1257 µm) for the Cirrus. The mean SL-TISA was 204.4 µm2+/-99.1µm2 (423.0-447.1 µm2) for the Optovue and 210.0µm2+/-107.2µm2 (33.7-497.7 µm2) for the Cirrus. The measurements between devices were highly correlated for both SL-AOD (R2=0.928, intraclass correlation coefficient (ICC) = 0.952) and SL-TISA (R2=0.867, ICC = 0.963) The mean percentage differences between the SD-OCT devices for the SL-AOD and SL-TISA measurements were 2.1% and 2.3% respectively, with coefficients of variation (CV) of 1.0 and 1.0, respectively. Inter-grader agreement was excellent for both devices, for both SL-AOD (CV= 1.3 Cirrus, CV=1.2, Optovue) and SL-TISA (CV= 1.2, Cirrus, CV=1.2, Optovue). No differences in inter-instrument or inter-grader agreement were observed between normal and glaucomatous eyes.
Novel Schwalbe’s line-based angle metrics showed excellent agreement between two different SD-OCT devices and between graders. These findings are promising for the use of these parameters in clinical studies, and suggest that multiple SDOCT devices may be used in the context of the same trial.
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