Longitudinal changes in optical coherence tomography angiography (OCTA) parameters versus retinal nerve fiber layer (RNFL) in glaucomatous and non-glaucomatous eyes

Abstract

Purpose : This study explores the longitudinal rates of change between peripapillary optical coherence tomography angiography (OCTA) parameters and retinal nerve fiber layer thickness (RNFL) of glaucomatous and non-glaucomatous eyes.

Methods : A retrospective, longitudinal study collected 6x6mm optic disc OCTA scans (Cirrus HD-OCT 5000) of glaucomatous and non-glaucomatous eyes with at least 2 visits between 12 to 24 months apart. Non-glaucomatous eyes included healthy and glaucoma suspects from an academic glaucoma clinic. A commercially provided automatic segmentation software was used to create en face OCTA images of the radial peripapillary capillary (RPC) layer. Images with poor quality, segmentation error or motion artifacts were excluded. Furthermore, subjects with non-glaucomatous optic neuropathy, cystoid macular edema, diabetic retinopathy, and other retinal disease were excluded. Images were quantified using a research-oriented quantification software to measure OCTA parameters: vessel area density (VAD), vessel skeleton density (VSD), and flux; a commercial quantification software measured perfusion density (PD) and flux index (FI). RNFL scans (Cirrus HD-OCT 5000) were also collected. The rates of change of OCTA parameters and RNFL were estimated using multivariable linear mixed-effects models.

Results : RPC OCTA images from 151 eyes of 96 subjects (81 non-glaucomatous eyes and 70 glaucomatous eyes) were included. RNFL OCT scans from 139 eyes of 87 subjects (78 non-glaucomatous and 61 glaucomatous eyes) were included. With a mean follow-up of 16 months, there was significant reduction in all OCTA parameters for both non-glaucomatous and glaucomatous eyes (Table 1) with a trend of faster reduction in the glaucomatous group. In contrast, there was no significant change in RNFL over time for either the non-glaucomatous or glaucomatous eyes.

Conclusions : OCTA images of the RPC layer showed significant annual rates of decrease in vessel parameters in both non-glaucomatous and glaucomatous eyes followed for 12-24 months. In contrast, the rate of change in RNFL thickness of the same eyes within the same time period was not significant. OCTA may have greater clinical utility than RNFL for monitoring progression in eyes at risk for and with glaucoma.

This is a 2021 ARVO Annual Meeting abstract.