Radial Peripapillary Capillary Plexus Perfusion and Regional Visual Field Loss in Glaucoma

Abstract

Purpose : To analyze the relationship between radial peripapillary capillary plexus (RPCP) capillary density and visual field (VF) in glaucoma using optical coherence tomography angiography (OCTA).

Methods : 41 primary open angle glaucoma (POAG) and 38 age-matched normal participants were analyzed in this observational study. One eye of each participant was imaged by 4.5×4.5 mm peripapillary OCTA scan using the AngioVue (Optovue, Inc.). The RPCP en face angiogram, which was obtained by the maximum flow projection in retinal nerve fiber layer (NFL), was divided into 8 sectors that follow the trajectory of nerve fibers and corresponds to a VF sectoral division scheme (Fig.1). The capillary density (CD), defined as the percentage area occupied by flow pixels after excluding large vessels, was calculated from a 4×4 mm square excluding optic disc using a reflectance-compensated algorithm. RPCP CD and retinal NFL thickness were converted to a percent loss relative to the normal average. The VF total deviation dB values at each sector were converted to percent loss (% loss = 100*(1-10[^dB/10])).

Results : The participants in glaucoma group were 64±10 years old, with VF MD -5.5±4.4 dB.The overall average loss for VF, RPCP and NFL were 38%±28%, 34%±21%, and 29% ±16%, respectively. Focal capillary dropout could be visualized in the RPCP angiogram of glaucomatous eyes (Fig. 1). Sector 4 had the greatest mean percent loss for all parameters. VF was highly correlated with both NFL thickness and RPCP CD in sector 4 (Fig. 2A, 2B, linear regression, the intercept was fixed at origin). In other sectors, RPCP CD correlated with VF from 0.408 to 0.816 (Pearson r, all P< 0.008) (Fig.2).

Conclusions : There is excellent correlation between RPCP, NFL, and VF loss when measured in corresponding sectors and converted to the same linear scale. Structural and angiographic OCT parameters may be useful in assessing the location and severity of glaucoma damage.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Figure 1. Map of corresponding sectors between RPCP capillary density (CD) loss and VF sensitivity loss in a glaucomatous eye.

 

Figure 2. Relationship between VF loss, NFL thickness and RPCP capillary density in each sector. Table cells display Pearson’s r (P value). Individual POAG eye values were plotted for sector 4, which had the worst damage.