Degree and Location of Retinal Capillary Closure Indicate ETDRS grading of Non Proliferative Diabetic Retinopathy

Abstract

Purpose : To explore the use of widefield OCTA (Swept-source OCTA PlexElite) to identify capillary closure in different regions of the retina (perifovea vs mid-periphery) in diabetes type 2, and its correlation with ETDRS severity stages.

Methods : 105 eyes from diabetic type 2 patients (66.6±7.9yrs) were imaged with the PlexElite 9000 (Zeiss, Dublin,CA) using Angio 15x9mm and Angio 3x3mm protocols. Data was processed by the Density Quantification of Averaged Data v0.3.5 algorithm available on the Advanced Research Imaging portal which uses multi-layer segmentation and calculates vascular density metrics for Superficial Capillary Plexus (SCP) and Deep Capillary Plexus (DCP). For retinal mid-periphery, 3 extra concentric rings were added to the standard 9 ETDRS areas. Images were checked for quality:signal strength ≥6, minimal motion artefacts and no evidence of defocus. Diabetic eyes were classified using the ETDRS severity scale, Grade 10-15(n=16), 20(n=17), 35(n=37), 43(n=15) and 47 to 65(n=14). Skeletonized Vessel Density (VD) measurements from diabetic patients were compared to an age matched healthy control population (n=28; 58.7±17.9yrs).

Results : Retinal capillary closure (CC) diabetes type 2 patients with mild ETDRS levels (10-35), predominates in the parafoveal region, with SCP VD values of 13.2±1.6 in ETDRS 10-20 (p<0.001) and 12.4±2 in ETDRS 35 (p<0.001), when compared with the healthy control population (14.6±1.1).
The CC extends to the retinal mid-periphery in the more severe ETDRS stages, with DCP VD values of 10.8±6.4 in ETDRS 43-47 (p=0.002) and 10.1±4.6 in ETDRS 53-61 (p=0.013) comparing with healthy control population.
Involvement of one or more retinal quadrants correlate with increase in ETDRS grade severity and allow discrimination between different ETDRS levels (see table 1). The 3x3mm acquisition protocol identifies well the initial DR stages (10-35), whereas 15x9 mm widefield SS-OCTA acquisitions of the midperiphery differentiates the more severe ETDRS levels.

Conclusions : Retinal CC, quantified by SS-OCTA, allows the identification and separation of different ETDRS levels, by combining 3x3mm and 15x9mm acquisitions and considering the number of retinal quadrants affected. SS-OCTA metrics of retinal CC, allowing measurements to be performed in the macula and in more retinal peripheral regions, may offer an objective and easier alternative to ETDRS severity grading.

This is a 2021 ARVO Annual Meeting abstract.