OCT Angiography Vessel Density in Normal, Glaucoma Suspects and Glaucoma Eyes: Structural and Functional Associations in the Diagnostic Innovations in Glaucoma Study (DIGS)

Abstract

Purpose : To assess vessel density measurements using optical coherence tomography angiography (OCTA) in normal, glaucoma suspects, and primary open angle (POAG) eyes and to characterize the relationship between vessel density and other quantitative structural and functional measurements.

Methods : 261 eyes of 164 DIGS participants with good quality OCTA images according to the Shiley Eye Institute Imaging Data Evaluation and Analysis (IDEA) Reading Center protocol were included. Using the Optovue AngioVue imaging system optic nerve head images (4.5 x 4.5 mm scan field size) were obtained in 124 POAG eyes, 87 glaucoma suspects, and 50 normal eyes. OCTA retinal vasculature information was characterized as a vessel density map, and as vessel density (%), calculated as the percentage area occupied by flowing blood vessels in the measured region. For this report, we analyzed two vessel density measurements in two regions extracted from the retinal nerve fiber layer (RNFL): 1) circumpapillary vessel density (cPVD) measured in a 750-μm-wide elliptical annulus around the disc; and 2) enface vessel density (EVD) measured over the entire image. Linear regression with generalized estimating equation (GEE) models were used to assess the relationship between vessel density, visual field mean deviation (VF MD) and spectral domain optical coherence tomographic (SD-OCT) RNFL thickness and adjusting for within-patient inter-eye correlations.

Results : Compared to POAG eyes, normal eyes demonstrated a denser microvascular network within the RNFL (Figure 1). Vessel density was higher in normal eyes followed by glaucoma suspect and POAG eyes for EVD (56.5%, 51.4% and 46.1%, respectively) and for cPVD (64.2%, 60.7%, 55.1%, respectively) (p<0.0001 for both). The association between OCTA measured cPVD and EVD and severity of VF damage measured as MD was stronger (R² = 0.49, and 0.47 respectively) than the association between RNFL thickness and VF MD (R²=0.30) (p<0.0001 for all) (Figure 2). cPVD and EVD also were correlated with RNFL thickness (R²=0.55, and 0.68 respectively) (p <0.0001 for both).

Conclusions : OCTA imaging provides quantitative assessment of the RNFL vasculature that is correlated with both structural and functional measurements. Longitudinal studies are needed to determine its value for diagnosing, staging, and monitoring glaucoma.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.