Blood Flow Speed of Retinal Microaneurysms in Eyes with Diabetic Retinopathy quantified by High Speed OCTA using Variable Interscan Time Analysis

Abstract

Purpose : To quantify the volume and blood flow speed of individual retinal microaneurysms (MAs) and investigate the relationship between blood flow speed and clinical characteristics in eyes with diabetic retinopathy (DR).

Methods : Macular OCT angiography (OCTA) imaging was performed on eyes with DR using a custom-built swept source OCT system operating at 600 kHz A-scan rate. The presence of MAs was determined based on B-scan OCT images, and each MA was classified according to intraluminal reflectivity, depth position within the retinal capillary plexus (RCP), and the presence of intraretinal fluid (IRF) surrounding MA. The boundaries of MA were manually traced and a three-dimensional (3D) MA mask was generated. Using variable interscan time analysis (VISTA), the VISTA flow speed (VFS) was evaluated as a surrogate marker of blood flow speed in MAs and RCPs.

Results : A total of 123 MAs were detected from 24 eyes of 20 DR patients with mean age of 58 ± 14 years old. The largest diameter, volume, and VFS of 123 MAs were 132.8 ± 37.7 μm and (7.87 ± 6.26) x10⁵ μm³, and 1.26 ± 0.53 ms^-1. MAs with medium and high intraluminal reflectivity (45% and 29% of 123 MAs, respectively) exhibited slower blood flow speed than MAs with low intraluminal reflectivity (1.19 ± 0.34, 1.14 ± 0.42, 1.52 ± 0.79 ms^-1, P<0.01), and were more commonly seen in MAs having slower blood flow speed than the retinal capillary plexus (P<0.01, Chi-Square test). Furthermore, MAs near IRF (54%) showed slower blood flow speed than MAs without surrounding IRF (1.15 ± 0.04 vs 1.37 ± 0.09 ms^-1; P=0.03).

Conclusions : VISTA OCTA is useful for measuring the blood flow speed of MAs and investigating the relationship to other structural information. The finding that decreased blood flow speed in MAs is correlated with the presence of IRF surrounding MAs may suggest that VFS could be a biomarker in diabetic macular edema management.

This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.

 

OCT angiography (OCTA) of a 66-year-old patient with mild non-proliferative diabetic retinopathy. (Left) OCTA of left eye showing multiple retinal microaneurysms (MAs) in the parafoveal area (green arrowheads). (Right) VISTA flow speed of MAs labeled as a, b, c and d were 1.52, 0.79, 0.88 and 1.27 ms^-1 respectively (white arrowheads). Other MAs were not visualized by OCTA alone but were detected by VISTA OCTA with 3D masking (pink arrows).