Microvascular impairment as a biomarker of diabetic retinopathy progression in the long-term follow up in type 1 diabetes.

This study aimed to explore differences in vascular and structural parameters using optical coherence tomography angiography in patients with type 1 diabetes (DM1) with mild signs of diabetic retinopathy (DR) over a two-year follow-up period. Parafoveal vessel density (PVD) and foveal avascular zone (FAZ) area were analyzed. The thickness of three predefined retinal slabs was measured, including the inner limiting membrane (ILM)-inner plexiform layer (IPL), IPL-inner nuclear layer (INL), and the IPL-outer nuclear layer (ONL). Twenty-two patients with DM1 and 21 controls were included. There was no significant difference in the FAZ area, perimeter and acircularity index between cohorts over time. Baseline superficial capillary plexus PVD was approximately 10% lower in patients with diabetes than in controls (p = 0.001), and was 12% lower at 2 years (p = 0.002). There was no difference in the annual linear trend between the groups (- 0.5% in diabetics vs. controls, p = 0.736). Baseline deep capillary plexus (DCP) PVD was slightly lower in diabetics than in controls (- 4.4%, p = 0.047) and the difference increased at 2 years (- 12.6%, p < 0.001). The annual linear trend was - 2.7% in diabetic patients compared to controls (p = 0.009)