Repeatability of swept-source optical coherence tomography angiography (SS-OCTA) metrics in healthy and glaucomatous eyes

Abstract

Purpose : To evaluate the intra-visit variability of quantitative measurements of SS-OCTA metrics.

Methods : One eye each from subjects with glaucoma and healthy controls were prospectively recruited from four sites. If two eyes were eligible, one eye per subject was designated randomly as the study eye. Each eye was imaged using the Angio 6x6 mm scan centered on the macula and centered on the optic disc on PLEX® Elite 9000 (ZEISS, Dublin, CA). Scans were repeated at each location on each device 3 times per visit, and the subjects were expected to complete 3 visits within one month.

Data were processed on the Advanced Imaging Network Hub using the algorithms: a) “Peripapillary Nerve Fiber Layer Microvasculature Density v0.9”, which quantifies microcirculation (with large vessels removed) in the radial peripapillary capillary layer, summarizing data over an annulus centered at the optic disc and b) “Superficial and GCIPL analysis v0.5”, which quantifies microcirculation in the superficial slab, summarizing data over the ETDRS grid centered on the macula.

Perfusion density (PD) is defined as the total area of perfused microvasculature per unit area. Flux index (FI) is defined as the total weighted area of perfused microvasculature per unit area in a region of measurement. The weight is the normalized flow intensity corresponding to each pixel. Vessel density (VD) is defined as the length of perfused microvasculature per unit area.

Intra-visit variability was determined by averaging the within-subject variance across visits for all eyes. The square root of this variance is the repeatability standard deviation.

Results : 33 healthy eyes (mean age 56.8, SD 11.5 years) and 31 eyes with glaucoma (mean age 61.1, SD 11.5) were imaged.

Table 1 shows the mean and coefficient of variance (CV) for legacy segmentation for disc-centered PD and FI measurements, which ranged from 1.7% to 3.2%. Table 2 shows the mean and CV for macula-centered VD and PD measurements, which ranged from 8.8% to 16.0%.

Conclusions : Coefficients of intra-visit variation are acceptable for both macula-centered and optic disc-centered SS-OCTA metrics, with optic disc-centered metrics showing excellent intra-visit variation. These parameters may have clinical utility for monitoring glaucomatous damage.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Table 1. Summary of optic disc-centered OCTA metrics

 

Table 2. Summary of macula-centered OCTA metrics