Comparing volumetric 3D versus standard 2D quantification of capillary ischemia in diabetic eye disease using optical coherence tomography angiography

Abstract

Purpose : To compare the effectiveness of volumetric (3D) against standard 2D measurements of ischemia for distinguishing early stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA).

Methods : We imaged 82 eyes of 82 patients (age 51.0 ± 11.9 y) including 27 healthy controls, 31 eyes with diabetes (DM) without DR, and 24 with mild non-proliferative DR (NPDR) using OCTA. We obtained 2D scans and 3D volumes of the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP). From 2D and 3D scans, we calculated geometric perfusion deficits (GPD), which define areas of retinal ischemia as those located farther than a set distance from the nearest blood vessel. For the GPD parameter, we compared the performance of a 20 mm vs. 30 mm distance threshold.

Results : Based on 2D scans, eyes with mild NPDR had significantly higher GPD in all 3 retinal capillary layers, indicating worse ischemia, when compared to either healthy controls or DM without DR, regardless of which distance threshold (20 mm or 30 mm) was used to define GPD (all p < 0.05). On the other hand, DM without DR showed no significant difference from healthy eyes in 2D images. Interestingly, when we looked at 3D volumes, DM without DR eyes had significantly greater DCP GPD than healthy eyes only when a GPD threshold of 20 mm was used (p < 0.05), but not with a 30-mm threshold (p = 0.057, Figure D).

Conclusions : Using the same stringent threshold (20 mm), 3D OCTA imaging detects significant DCP perfusion defects in diabetic eyes even before the onset of retinopathy, while traditional 2D OCTA does not. 3D volumetric scans of the retina may therefore be more sensitive to early ischemia in diabetes.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Volumetric OCTA scans (B, C) may be more sensitive for retinal ischemia in early diabetes (DM) than standard 2D scans (A). Eye of a 63-y.o. female with DM and no retinopathy. White = vessel skeletons, blue = areas within 20 μm (perfused), yellow = GPD defined as > 20 μm from vessel, red = GPD defined as > 30 μm from vessel. B and C are B-scans representing vessels (B) and the 3-dimensional GPD map (C) at corresponding to the white dashed line. Green asterisks indicate areas of ischemia in the deep capillary plexus (DCP) that are more clearly visualized in 3D. D: Comparison of DCP GPDs in healthy, DM w/o DR, and mild nonproliferative DR groups. *p < 0.05, **p < 0.01.