Reproducibility of Scleral Vasculature Measurements with Anterior Segment OCT Angiography in POAG

Abstract

Purpose : The anterior segment (AS) fluid dynamics is established as a primary site for impairment and a target for treatment in glaucoma. In vivo, non-invasive visualization and quantification of scleral vessels (SV) might provide important clinical insight for glaucoma management. This study aims to assess the reproducibility of SV measurements using AS-OCT angiography (OCTA) in subjects with primary open angle glaucoma (POAG).

Methods : Subjects with POAG underwent a comprehensive clinical examination, visual field (VF) testing and imaging with PlexElite SS-OCT (Zeiss, Dublin, CA). Images were acquired using the Anterior Segment scanning protocol and a prototype anterior segment attachment developed by the manufacturer. Multiple OCTA scans were acquired at 200 kHz in a 6mm x 6mm x 6 mm (500x500x3072 voxels) region with 2 repetitions for capturing blood flow motion contrast. Scans were centered on the corneal limbus, nasally and temporally. Enface projection images were denoised and contrast enhanced to improve vessel visualization. A region of interest (ROI) spanning a circumferential arch length of 3mm with a diameter of 1.6mm was set at the bottom of Schlemm’s canal (SC). Additional Frangi, skeleton and perfusion filters were applied for quantifying the SV from the OCTA scan (Figure). Intraclass correlation coefficient (ICC) and within subject coefficient of variance (WSCoV) were performed to assess reproducibility of the SV measurements.

Results : Twenty eyes (20 subjects) qualified for the study according to the motion and imaging artifacts criteria. Subjects were age 66.6 ± 11.1 yrs (Mean ± SD), with IOP=13 ± 3.8 mmHg, VF mean deviation (MD) -9.0 ± 9.5 dB, and average RNFL thickness of 73 ± 11.7 µm. OCTA vessel parameters were compiled from nasal and temporal scans. ICC for OCTA measurements were within moderate to good reliability range (Table). Likewise, WSCoV exhibited good reproducibility.

Conclusions : SV-AS-OCTA measurements acquired in the vicinity of the SC are reproducible in POAG eyes. The role of SV-AS-OCTA measurements in glaucoma management merits further investigation.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.