Perspective for a Conversion Model of OCTA Metrics in Different Diabetic Retinopathy Stages: Angiovue vs Angioplex

Abstract

Purpose : To explore measurements variability between 2 different OCTA devices and to develop a conversion model that translates vascular metrics into a standardized and comparable value in patients with different stages of Diabetic Retinopathy (DR).

Methods : A cross-sectional study was conducted in 101 subjects (n=196 eyes) with type 2 diabetes (68.1±8.1yrs). Each eye underwent 3x3mm OCTA scans centered at fovea in AngioVue (Optovue RTVue, Optovue Inc, CA, USA) followed by Angioplex (Cirrus HD-OCT 5000, Zeiss Meditec Inc). The binarized Vessel Density (bVD) in the Inner Ring (3mm ø) was collected from the superficial capillary plexus (SCP) images of both devices. Agreement between AngioVue and Angioplex measurements was assessed by Intraclass Correlation Coefficient (ICC) and Bland-Altman plots. A conversion equation was established to transform bVD values from Angiovue into Angioplex-equivalent values. This equation was built using repeated-measures models with generalized estimating equations to account for the correlation in participants with 2 study eyes, with Angioplex measurement as the dependent variable and AngioVue measurement as the independent variable and adjusted for disease severity level.

Results : Twenty-four eyes with no DR (ETDRS level 10-20), 67 with mild DR (ETDRS level 35), 54 with moderate DR (ETDRS level 43) and 51 with moderate-severe DR (EDTRS level 47-53) were included. Binarized VD values measured by AngioVue were significantly higher than by Angioplex (42.9±4.8% vs 35.6±3.3%; p<0.001). ICC between both devices showed a poor agreement of this metric (0.174 [-0.083, 0.444]). Regarding the conversion model, the following equation was derived: Angioplex bVD= (Angiovue bVD x 0.40) + 18.54. With this equation, 81% of the Angioplex-equivalent bVD values fell within 10% of the real Angioplex measurements. The difference between converted and real values of bVD was less than 8.5 bVD units.

Conclusions : Angiovue and Angioplex OCTA devices use distinct algorithms to detect retina binarized VD. In this study, we propose a conversion model to obtain comparable bVD measurements in eyes of subjects with diabetes and with distinct levels of ETDRS DR severity. This conversion model may allow to pool bVD data from different OCTA instruments, allowing comparison of results within and between groups in clinical trials using both instruments.

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