Perivenular Capillary Rarefaction in Diabetic Retinopathy: Interdevice Characterization and Association to Clinical Staging

Abstract

Purpose: Geometric perfusion deficit (GPD) is a newly described OCT angiography (OCTA) parameter identifying the total area of presumed retinal ischemia. The aim of our study is to characterize differences in GPD and other common quantitative OCTA parameters between macular full field, perivenular zones, and periarteriolar zones for each clinical stage of nonproliferative diabetic retinopathy (DR) and to assess the influence of ultrahigh-speed acquisition and averaging on the described differences.

Design: Prospective observational study.

Participants: Forty-nine patients, including 11 (22.4%) with no sign of DR, 12 (24.5%) with mild DR, 13 (26.5%) with moderate DR, and 13 (26.5%) with severe DR. Patients with diabetic macular edema, proliferative DR, media opacity, head tremor, and overlapping retinal diseases or systemic diseases influencing OCTA were excluded.

Methods: OCT angiography was performed 3 times for each patient: 1 using Solix Fullrange single volume (V1) mode, 1 using Solix Fullrange 4 volumes mode with automatically averaged scan (V4), and 1 using AngioVue.

Main outcome measures: Full macular, periarteriolar, and perivenular perfusion density (PD), vessel length density (VLD), vessel density index, and GPD for both the superficial capillary plexus (SCP) and deep capillary plexus (DCP).

Results: In patients showing no sign of DR, PD and VLD were significantly lower in the perivenular area in both the DCP and SCP using V1 and V4, whereas GPD was significantly higher in the perivenular zone in the DCP and SCP with all 3 devices. In patients with mild DR, all 3 measurements (PD, VLD, and GPD) were significantly different in the perivenular zone with all 3 devices. In patients with moderate DR, PD and VLD were lower in the DCP and SCP when measured with V1 and V4. Moreover, GPD was higher in the perivenular zone in the DCP with all 3 devices, whereas only V4 detected a difference in the SCP. In severe DR, only V4 detected a lower PD and VLD and a higher GPD in the DCP of the perivenular zone. V4 also detected a higher GPD in the SCP.

Conclusions: Geometric perfusion deficit highlights prevalent perivenular location of macular capillary ischemia in all stages of DR. In severe DR patients, only averaging technology allows detection of the same finding.

Financial disclosures: The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Keywords: Capillary ischemia; DCP, deep capillary plexus; DR, diabetic retinopathy; Diabetic retinopathy; GPD, geometric perfusion deficit; Geometric perfusion density; OCT angiography; OCTA, OCT angiography; PD, perfusion density; ROIs, regions of interest; SCP, superficial capillary plexus; V1, single volume; V4, 4 volumes mode with automatically averaged scan; VDI, vessel density index; VLD, vessel length density.

Figure 1

Upper left: Raw fovea centered 3 × 3 mm OCT angiography (OCTA) of the superficial capillary plexus of a patient from the moderate diabetic retinopathy subgroup. Acquired using Solix single volume mode. Upper middle: Binarized and thresholded version of upper left image (used for perfusion density [PD] and geometric PD calculation of full macular data). Upper right: Raw OCTA with arterioles highlighted in red and venules highlighted in blue. Lower left: Thresholded arterioles used for arteriolar region of interest (ROI) calculation. Lower right: Thresholded venules used for venular ROI calculation. .

Figure 2

Binarized thresholded 3 × 3 mm en face OCT angiography of the superficial capillary plexus of a patient from the mild diabetic retinopathy (DR) (upper panels) and moderate DR (lower panels) study subgroups acquired using Solix single volume mode. Left image shows arterioles highlighted in red and geometric perfusion density (GPD) in the arteriolar region of interest (ROI) (within 100 mm from every arteriolar pixel) highlighted in green. In the upper panels showing a case of mild DR, the periarteriolar GPD calculated for this image is 11.80%. Right image shows venules highlighted in blue and GPD in the venular ROI (within 100 mm from every venular pixel) highlighted in yellow; perivenular GPD calculated for this image is 12.91%. In the lower panels showing a case of moderate DR, the periarteriolar GPD calculated for this image is 13.34%. Right image shows venules highlighted in blue and GPD in the venular ROI (within 100 mm from every venular pixel) highlighted in yellow; perivenular GPD calculated for this image is 13.61%.

Figure 3

Full macular deep capillary plexus (DCP) geometric perfusion density (GPD) in diabetic patients with no diabetic retinopathy (DR) (upper left), mild DR (upper right), moderate DR (lower left), and severe DR (lower right). V1 = single volume; V4 = 4 volumes mode with automatically averaged scan.