Evaluating Blood Flow Speed in Retinal Microaneurysms Secondary to Diabetic Retinopathy Using Variable Interscan Time Analysis OCTA

Abstract

Purpose: To quantify the blood flow speed within retinal microaneurysms (MAs) and investigate the relationship between blood flow speed and clinical characteristics in eyes with diabetic retinopathy (DR). Methods: Variable interscan time analysis (VISTA) quantifies blood flow speed in the vasculature by measuring how fast optical coherence tomography (OCT) angiography (OCTA) saturates for different interscan times. Macular OCTA imaging was performed in eyes with DR using a high-speed swept-source OCT prototype instrument operating at a 600-kHz A-scan rate. The presence of MAs was determined using OCT B-scans, and three-dimensional MA masks were generated. VISTA flow speed (VFS) was determined within MAs and the retinal capillary plexus (RCP). Intraluminal reflectivity, axial location within the RCP, and the presence of intraretinal fluid (IRF) around the MAs were evaluated. Results: A total of 123 MAs were detected from 24 eyes of 20 patients with DR. Mean VFS was 1.26 ms-1 (95% confidence interval, 1.16-1.35). MAs with medium and high intraluminal reflectivity had slower VFS than those with low intraluminal reflectivity (P < 0.01) and often had slower VFS than the RCP (P < 0.01). Sixty-six MAs were located near IRF and had slower VFS than the other 57 MAs without surrounding IRF (1.16 ms-1 vs. 1.37 ms-1; P = 0.03). Conclusions: VISTA OCTA can assess blood flow speed of MAs in relation to other structural features in DR. Decreased blood flow speed in MAs is correlated with the presence of IRF around MAs. Translational Relevance: We offer a new method that quantifies the blood flow speed of MAs to study the development of diabetic macular edema.