Evaluation of foveal microvasculature changes by optical coherence tomography angiography in eyes of pacientes with type 2 diabetes diagnosed more than 5 years ago without clinical signs of diabetic retinopathy versus patients without diabetes

Background: The aim of this study was to compare vascular density (VD) and foveal avascular zone (FAZ) using optical coherence tomography angiography (OCTA) in patients with type 2 diabetes mellitus (DM) without signs of diabetic retinopathy (DR) with non-diabetic patients. Methods: A total of 26 type 2 DM and 17 non-diabetic subjects were included in a case-control study. All subjects underwent OCTA (DRI OCT-1 SS TRITON PLUS; Topcon, Tokyo, Japan). Average vessel density (VD) in superficial capillary plexus (SCP), deep capillary plexus (DCP), FAZ area (mm2) in SCP, and FAZ area (mm2) in DCP were included in the analysis. The comparisons were evaluated using the analysis of variance (ANOVA) and Tukey’s post hoc test. Results: Parafoveal vessel density in both SCP and DCP decreased in eyes without clinical DR compared to non-diabetic controls (p < 0.001). Statistical significance was also observed when comparing controls with patients diagnosed with type 2 DM 5-10 years ago (p < 0.001), controls with patients diagnosed with type 2 DM more than 10 years ago (p < 0.001), and patients diagnosed with type 2 DM 5-10 years ago with those diagnosed more than 10 years ago (p < 0.001). In addition, the FAZ area in both plexuses increased in case eyes compared to controls (p < 0.001). However, there was no significance of FAZ area in SCP when comparing cases diagnosed between 5-10 years ago to those diagnosed more than 10 years ago (p = 0.06). Conclusion : It was demonstrated that OCTA can detect preclinical DR before the manifestation of clinically apparent retinopathy in diabetic eyes, especially in long-term diagnosed disease. In type 2 DM patients without DR, SCP and DCP were affected, and the changes were progressive and significant with increasing time to diagnosis. Our results suggest that OCTA may be a promising tool for regular screening of diabetic eyes for DR.