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Ashley Nguyen, Quoc Ho, Francisco J. Lopez, Kevin Kerr, Susan Schneider, Jingyuan Yang, Margot L Goodkin, Michelle Y. Chen; A Novel Iridocorneal Angle Measurement Technique: Assessment of Inter- and Intra-Scorer Variability. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1699.
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Iridocorneal angle sizes were evaluated using a novel method that accounts for local morphological variations of the iris using anterior segment optical coherence tomography (AS-OCT). The purpose of this study is to determine inter- and intra-scorer variability of this technique and compare this method to previously reported approaches of iridocorneal angle size assessment.
AS-OCT images of subjects (n=74) with open angle glaucoma and/or ocular hypertension from a multicenter noninterventional study (NCT01540370) were included in this retrospective analysis. Gonioscopic assessment of the iridocorneal angle was performed by a site investigator using Spaeth Peripheral Iris Curvature (SPIC). In this study, measurements of the distance from Schwalbe’s line to the surface of the iris were conducted independently by two scorers using ImageJ software (v1.51k) to determine angle width (AS-OCTAW). Using R software (v3.4.2) under RStudio, inter- and intra-scorer variability of AS-OCTAW measurements was determined. Bland-Altman (BA) plots were constructed and mean percent differences (MPD) calculated. Coefficients of variation (CV), and intraclass correlation coefficients (ICC) were evaluated. Results were compared to previously reported inter- and intra-scorer variability of Schwalbe’s Line Angle Opening Distance (SL-AOD) by Pan et al., 2015. A subgroup analysis of AS-OCTAW in subjects with steep SPICs was compared to SL-AOD.
Mean AS-OCTAW was 490 ± 185µm for scorer 1 and 495 ± 189µm for scorer 2. Inter- and intra-scorer variability was low (CV 1.44% ± 0.13% and CV 1.04% ± 0.1%, with good equivalence evaluated by BA and MPD of 2.03% and 1.47%, respectively). ICCs showed strong inter- and intra-scorer correlations at > 0.99 for both. AS-OCTAW showed less variability when compared to reported SL-AOD variability (inter- MPD 15.47%, ICC 0.94; intra- MPD 4.28%, ICC 0.995). For steep SPIC grades, SL-AOD had a larger mean and slightly higher variability compared to AS-OCTAW (n=15, mean SL-AOD 462 ± 118 µm, mean AS-OCTAW 389 ± 89 µm).
Inter- and intra-scorer variability with AS-OCTAW is low, suggesting high repeatability for this method. In comparison to SL-AOD, AS-OCTAW provides more consistent iridocorneal angle measurements. In subjects with a steep SPIC grade, AS-OCTAW accounted for morphological differences in iridocorneal anatomy.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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