Peripapillary Vessel Density as a Glaucoma Biomarker throughout the Glaucoma Severity Spectrum

Abstract

Purpose : Structural parameters are commonly used to track the progression of glaucoma. In this study, we investigated if peripapillary vessel density (VD), measured by optical coherence tomography angiography (OCTA), is associated with glaucoma severity and thus may be used to track glaucoma progression.

Methods : 82 eyes of 50 subjects ranging from glaucoma suspect to severe glaucoma were included in the study. Subjects with diabetes, vascular disease, or using medications known to affect visual field were excluded. 3x3 mm optic nerve head (ONH) OCTA images were obtained on all subjects using a Cirrus HD-OCT Angioplex (Zeiss, Dublin, CA) device. VD was calculated using the native software on the device. Best-fit models (linear regression or piecewise regression with Davies test to detect tipping points) were used to describe the associations between VD and RNFL and GCIPL thicknesses, rim area, cup-to-disc (C/D) ratio, and visual field mean deviation (MD).

Results : The median age was 61 years (range 20 to 86) with a median MD of -1.4dB (range 2.3 to -33.5dB) and a mean RNFL thickness of 78.4μm (SD=14.2, range 43 to 118μm). Statistically significant linear associations were found between peripapillary VD and RNFL thickness, GCIPL thickness, and rim area (all p<0.001; Figure 1). Association between VD and C/D ratio and MD showed a tipping point at 0.73 (p=0.005) and -3.3dB (p<0.001), respectively (Figure 1). In advanced glaucoma, the rate of change in C/D ratio slowed, while the VD measurements varied over a wide range. In early glaucoma, there was limited change in MD values, again with a wide range in VD measurements. Coefficients of determination (R²) were statistically significant between peripapillary vessel density, structural parameters, and MD (all p≤0.001; Table 1).

Conclusions : Peripapillary VD is significantly associated with conventional glaucoma severity biomarkers. The wide dynamic range of VD in early and advanced disease indicates that VD may be a useful biomarker at stages where diagnosis and progression detection is particularly difficult. Further longitudinal analysis is warranted.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1: Peripapillary VD against RNFL thickness, GCIPL thickness, rim area, average C/D ratio, and MD.

 

Table 1: Coefficients of determination between peripapillary vessel density, structural biomarkers, and MD.