Relationship between Optical Coherence Tomography Angiography Vessel Density and Severity of Visual Field Loss in Glaucoma

Abstract

Purpose: To evaluate the association between vessel density measurements using optical coherence tomography angiography (OCT-A) and severity of visual field loss in primary open-angle glaucoma.

Design: Observational, cross-sectional study.

Participants: A total of 153 eyes from 31 healthy participants, 48 glaucoma suspects, and 74 glaucoma patients enrolled in the Diagnostic Innovations in Glaucoma Study.

Methods: All eyes underwent imaging using OCT-A (Angiovue; Optovue, Fremont, CA), spectral-domain OCT (Avanti; Optovue), and standard automated perimetry (SAP). Retinal vasculature information was summarized as vessel density, the percentage of area occupied by flowing blood vessels in the selected region. Two measurements from the retinal nerve fiber layer (RNFL) were used: circumpapillary vessel density (cpVD) (750-μm-wide elliptical annulus around the optic disc) and whole-image vessel density (wiVD) (entire 4.5×4.5-mm scan field).

Main outcome measures: Associations between the severity of visual field loss, reported as SAP mean deviation (MD), and OCT-A vessel density.

Results: Compared with glaucoma eyes, normal eyes demonstrated a denser microvascular network within the RNFL. Vessel density was higher in normal eyes followed by glaucoma suspects, mild glaucoma, and moderate to severe glaucoma eyes for wiVD (55.5%, 51.3%, 48.3%, and 41.7%, respectively) and for cpVD (62.8%, 61.0%, 57.5%, 49.6%, respectively) (P < 0.001 for both). The association between SAP MD with cpVD and wiVD was stronger (R2 = 0.54 and R2 = 0.51, respectively) than the association between SAP MD with RNFL (R2 = 0.36) and rim area (R2 = 0.19) (P < 0.05 for all). Multivariate regression analysis showed that each 1% decrease in wiVD was associated with 0.66 decibel (dB) loss in MD and each 1% decrease in cpVD was associated with 0.64 dB loss in MD. In addition, the association between vessel density and severity of visual field damage was found to be significant even after controlling for the effect of structural loss.

Conclusions: Decreased vessel density was significantly associated with the severity of visual field damage independent of the structural loss. Optical coherence tomography angiography is a promising technology in glaucoma management, potentially enhancing the understanding of the role of vasculature in the pathophysiology of the disease.

Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Vessel Density Map of the Retinal Nerve Fiber Layer showing microvasculature in healthy (most dense), mild, moderate and severe glaucoma (least dense) eye. Top row: Vessel density extracted map with elliptical circumpapillary (cpVD) measurement region defined; Second row: Area vessel density color-coded map; Bottom row: Standard automated perimetry (SAP) visual field results showing corresponding visual field defects.

Figure 2

Boxplots illustrating the distribution of whole image vessel density (left) and circumpapillary vessel density (right) in healthy, glaucoma suspects, mild and moderate to severe glaucoma participants. The medians are represented by horizontal line in the gray box. Error bars represent the interquartile range.

Figure 3

Scatter plots illustrating the linear (grey line) and curvilinear (quadratic fit: dark lines) correlation between standard automated perimetry (SAP) mean deviation and optical coherence tomography angiography (OCT-A) whole image vessel density, circumpapillary vessel density, Spectral domain (SD) OCT average retinal nerve fiber layer (RNFL) thickness, and rim area measurements. *R2: Adjusted-R2 from the Linear Regression Model, § R2: Adjusted-R2 from the Quadratic Regression Model.

Figure 4

Scatterplots illustrating the linear (grey line) and curvilinear (quadratic fit: dark lines) correlation between standard automated perimetry (SAP) pattern standard deviation and optical coherence tomography angiography (OCT-A) whole image vessel density, circumpapillary vessel density, Spectral domain (SD) OCT average retinal nerve fiber layer (RNFL) thickness, and rim area measurements. *R2: Adjusted-R2 from the Linear Regression Model, § R2: Adjusted-R2 from the Quadratic Regression Model.