Abstract
Purpose :
Many retinal diseases differentially affect arteries and veins. We sought to develop a tool to non-invasively analyze arteriolar and venular connectivity of capillary plexuses in the healthy macula using optical coherence tomography angiography (OCTA), and examined clinical applications in eyes with neovascular pathology.
Methods :
20 eyes of 20 healthy controls (age 25.3 ± 2.2 years) were imaged with OCTA, and 3D volumes of the full retinal slab segmented into superficial (SCP), middle (MCP), and deep capillary plexuses (DCP). Large SCP vessels were classified as arterioles or venules by 2 graders. We implemented a custom watershed algorithm to identify arteriolar- and venular-connected capillaries by using the large SCP vessels as seed points for flooding the rest of the vascular network. We calculated A/V ratios of arteriolar- to venular-connected vessels and adjusted flow indices (AFI) for the SCP, MCP, and DCP.
We also analyzed 2 eyes of a patient with proliferative diabetic retinopathy (PDR) and 1 eye of a patient with macular telangiectasia (MacTel) to evaluate utility of this method in visualizing vascular connectivity to pathological neovascularization (NV).
Results :
In healthy eyes, MCP A/V ratio was significantly higher than the SCP and the DCP, indicating a higher proportion of arteriolar-connected vessels (all p < 0.001). Arteriolar-connected vessel AFIs were higher than venular-connected AFIs in the SCP, but this pattern reversed in the MCP and DCP, which had higher venular-connected AFIs than arteriolar (all p < 0.001).
In the PDR eyes, preretinal NV originated from venules, while intra-retinal microvascular abnormalities appeared as dilated capillary loops within the MCP connecting an arteriole and venule. In MacTel, diving SCP venules formed the epicenter of outer retinal NV.
Conclusions :
We developed an algorithm for assigning arteriolar and venular connectivity of retinal vessels. Healthy eyes showed increased MCP arteriolar connections but relatively slower arteriolar vs. venular flow velocity in the MCP and DCP, which may contribute to the unique vulnerability of these layers to ischemia in conditions like paracentral acute middle maculopathy (PAMM). In eyes with neovascular pathology, our findings were consistent with histopathologic studies. Further studies are needed to investigate utility of this method in PAMM and other vascular diseases.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.