Applications of optical coherence tomography angiography in glaucoma: current status and future directions

Abstract

Glaucoma is a leading cause of irreversible blindness worldwide, with its pathophysiology remaining inadequately understood. Among the various proposed theories, the vascular theory, suggesting a crucial role of retinal vasculature deterioration in glaucoma onset and progression, has gained significant attention. Traditional imaging techniques, such as fundus fluorescein angiography, are limited by their invasive nature, time consumption, and qualitative output, which restrict their efficacy in detailed retinal vessel examination. Optical coherence tomography angiography (OCTA) emerges as a revolutionary imaging modality, offering non-invasive, detailed visualization of the retinal and optic nerve head microvasculature, thereby marking a significant advancement in glaucoma diagnostics and management. Since its introduction, OCTA has been extensively utilized for retinal vasculature imaging, underscoring its potential to enhance our understanding of glaucoma's pathophysiology, improving diagnosis, and monitoring disease progression. This review aims to summarize the current knowledge regarding the role of OCTA in glaucoma, particularly its potential applications in diagnosing, monitoring, and understanding the pathophysiology of the disease. Parameters pertinent to glaucoma will be elucidated to illustrate the utility of OCTA as a tool to guide glaucoma management.

Keywords: glaucoma; glaucoma progression detection; optical coherence tomography angiography; retinal imaging; vessel density.

Figure 1

Illustration of optic disc-centered OCTA report captured by Triton DRI-OCT (Topcon, Inc., Tokyo, Japan) with 3 × 3 mm (A) and 6 × 6 mm (B) scan pattern. ILM, internal limiting membrane; BM, Bruch membrane; RPC, radial peripapillary capillary.

Figure 2

Illustration of macular-centered OCTA report captured by Triton, DRI-OCT (Topcon, Inc., Tokyo, Japan) with 3 × 3 mm (A) and 6 × 6 mm (B) scan pattern. ILM, internal limiting membrane; IPL, inner plexiform layer; INL, inner nuclear layer; BM, Bruch membrane.

Figure 3

Examples of quantification of OCTA metrics by our customized MATLAB (MathWorks, Natick, MA) program in superficial peripapillary area and superficial macular area. A series of OCTA metrics, including vessel diameter index (VDI), fractal dimension (FD), and vessel density (VD), were automatically calculated from the superficial OCTA image.

Figure 4

Correlation between OCTA, OCT, and visual field in normal eye, mild glaucoma, moderate glaucoma, and advanced glaucoma. Top layer: OCTA radial peripapillary capillary layer images (left) and OCT RNFL thickness map (right) at optic disk region; middle layer: OCTA superficial images (left) and OCT GCIPL thickness map (right) at macular region; bottom layer: visual field grayscale map (left) and pattern deviation map (right). ONH, optic nerve head; RNFL, retinal nerve fiber layer; GCIPL, ganglion cell inner plexiform layer; MD, mean deviation.