Longitudinal microvascular and neuronal retinal evaluation in patients with diabetes mellitus type 1 and 2 and good glycemic control

Purpose: To evaluate microvascular and neuronal changes over 3 years in patients with type 1/2 diabetes mellitus (DM1/DM2), good metabolic control and no signs of diabetic retinopathy (DR). Methods: In this prospective, longitudinal study, 20 DM1, 48 DM2 and 24 controls underwent macular OCT ant OCT-A at baseline and after 3 years. Following parameters were considered: thickness of the central macula (CMT), retinal nerve fiber layer (NFL), ganglion cell (GCL+/GCL++) complex; perfusion and vessel density (PD/VD) and fractal dimension (FD) at the superficial and deep capillary plexuses (SCP/DCP); choriocapillaris flow deficits (CC-FD); foveal avascular zone (FAZ) metrics. MATLAB and ImageJ were used for OCT-A scans analyses. Results: Mean HbA1c was 7.4 ± 0.8% in DM1 and 7.2 ± 0.8% in DM2 at baseline, with no change at 3 years. No eye developed DR. In longitudinal analyses, PD at SCP (p=0.03) and FAZ area and perimeter (p<0.0001) significantly increased in DM2 compared to other groups. No longitudinal changes occurred in OCT parameters. In comparisons within groups, DM2 had a significant thinning of GCL++ in the outer ring, decreased PD at DCP and CC-FD, an increase in FAZ perimeter and area in DCP; DM1 had an increase in FAZ perimeter in DCP (p<0.001 for all comparisons). Conclusion: Longitudinal data showed significant microvascular retinal changes in DM2. No changes were detected in neuronal parameters and in DM1. Longer and larger studies are needed to confirm these preliminary data.