Macular vascular complexity analysis of diabetes mellitus by swept-source optical coherence tomographic angiography

Purpose: This study was designed to evaluate the associations between retinal vascular complexity features, including fractal dimension (FD) and blood vessel tortuosity (BVT), and the severity of diabetic retinopathy (DR) by using optical coherence tomographic angiography (OCTA).Methods: In this prospective cross-sectional study, 1282 ocular-treatment-naive patients with type 2 diabetes mellitus (DM) (1059 without DR and 223 with DR) registered in the community of Guangzhou, China, were enrolled. OCTA was used to measure FD and BVT in the superficial capillary plexus (SCP) and the deep capillary plexus (DCP). Univariate and multivariate linear regression analyses were performed to analyze the correlation of FD and BVT in different layers with DR severity.Results: In this study, 1282 patients with DM (1282 eyes), with a mean age of 64.2 +/- 7.8 years, were included. FD in the DCP decreased and BVT in the DCP increased in patients with DR compared with those in patients without DR, even after adjusting for confounding factors (P< 0.05). Trend analysis showed a significant decrease in the FD values as the DR progressed, whereas the BVT progressively increased with worsening DR severity (P< 0.01). The FD in DCP had a statistically significant positive correlation with FD in SCP and a negative correlation with BVT in SCP and BVT in DCP in all of the participants, including the non-DR group, moderate DR group, and severe DR group (P< 0.01).Conclusions: FD and BVT determined using OCTA might be useful parameters for objectively distinguishing DR from non-DR and indicating DR progression.