Quantitative analysis of vascular complexity in OCTA of diabetic retinopathy

Diabetic retinopathy (DR) is a major ocular manifestation of diabetes. DR can cause irreversible damage to the retina if not intervened timely. Therefore, early detection and reliable classification are essential for effective management of DR. As DR progresses into the proliferative stage (PDR), manifestation of localized neovascularization and complex capillary meshes are observed in the retina. These vascular complex structures can be quantified as biomarkers of transition of DR from no-proliferative to proliferative stage (NPDR). This study investigates four optical coherence tomography angiography (OCTA) features, i.e. vessel complexity index (VCI), fractal dimension (FD), four-point crossover (FCO), and blood vessel tortuosity (BVT), to quantify vascular complexity to distinguish NPDR from PDR eyes. OCTA images from 20 control, 60 NPDR and 56 PDR patients were analyzed. The univariate analysis showed that, with the progression of DR, all four complexity features increased with statistical significance (ANOVA, P < 0.05). A posthoc study showed that, only VCI and BVT were able to distinguish between NPDR and PDR. A multivariate logistic regression identified VCI and BVT as the most significant feature combination for NPDR vs PDR classification.