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Jyotsna Maram, Xiaojing Pan, Ken Marion, Zhou Y Zhang, Srinivas R Sadda, Vikas Chopra; Effect of Angle of Incidence on Anterior Chamber Angle Metrics from Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2014;55(13):937.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the local variability of anterior chamber angle (ACA) metrics obtained by time domain (TD) and spectral domain (SD) optical coherence tomography (OCT).
Anterior segment OCT imaging was performed on 30 normal eyes using Visante TD-OCT and on 40 normal eyes using Cirrus SD-OCT. For Visante OCT, a single 16-mm line scan of the inferior angle with three slightly different rotations of 265, 270 and 275 was performed. For Cirrus OCT, a 5-line raster of the inferior angle was performed, centering the third scan line at the 6 o’clock position, with 0.25 mm between lines. ACA measurements were taken for angle opening distance (AOD) and trabecular iris space area (TISA) at 500/750 µm from the scleral spur for Visante OCT and at Schwalbe’s line (SL) for Cirrus OCT. Measurements between line scans for each device were compared and quantified.
For the Visante OCT at three different scan orientations, the mean difference in ACA metrics was 0.41±0.15 mm for AOD-500, 0.59±0.22 mm for AOD-750, 0.14±0.06 mm2 for TISA-500, and 0.27±0.1 mm2 for TISA-750. For three different scan positions with Cirrus OCT, the AOD-SL and TISA-SL showed mean differences of 0.85±0.32 mm and 0.33±0.15 mm2, respectively.
These findings suggest that small local changes in the position of the OCT line scan did not significantly alter ACA metrics in achieving reliable measurements. Given the absence of tracking and registration for current anterior segment OCT instruments, this observation is of relevance for longitudinal and dynamic studies of angle geometry.
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