Retinal Vascular Density and Thickness in Long-Term Type 1 Diabetes Without Visible Vascular Signs of Retinopathy

Background: This research seeks to evaluate alterations in blood flow and structural features within the superficial (SCP) and deep (DCP) retinal capillary plexuses, as well as the choriocapillaris (CC), in patients with type 1 diabetes (DM1) who have no diabetic retinopathy (DR) over a period of 4 years. Additionally, the study examines changes in total and inner retinal thickness. Methods: A prospective, longitudinal analysis was conducted using optical coherence tomography (OCT) and OCT angiography (OCTA), involving 25 eyes from 25 DM1 patients with a disease duration of over 15 years. Results: A significant rise in vascular density (VD) was observed in the SCP, with no changes in foveal avascular zone (FAZ) metrics. Minimal changes were noted in the DCP and CC. Morphological abnormalities were frequent, but few changes were noted over time. No major differences were found in overall retinal thickness or inner retinal layers. There was a negative correlation between disease duration and VD in the temporal area of the SCP, as well as between disease duration and GCL++ parafoveal thickness (from the inner limiting membrane (ILM) to the outer limit of the inner plexiform layer (IPL)), along with a reduction in GCL++ perifoveal thickness. Conclusions: In DM1 patients without DR, the SCP VD tends to increase over 4 years, with no notable changes in retinal thickness.