Purpose: To assess demographic, metabolic, and imaging predictors influencing microvasculature and photoreceptors changes over a 4-year follow-up in type 1 diabetes mellitus (DM1).
Methods: This prospective cohort study enrolled patients with DM1 with mild non-proliferative diabetic retinopathy. Complete medical records, glycosylated hemoglobin (HbA1c), optical coherence tomography angiography, and adaptive optics were collected for the 4 years of follow-up. The main outcome measures included perfusion density at the superficial capillary plexus (SCP) and deep capillary plexus (DCP), choriocapillaris (CC) flow deficits (FDs, %), cone density, linear dispersion index (LDi), and heterogeneity packing index (HPi).
Results: The SCP presented a dichotomic perfusion trend, with increasing PD at 1 and 2 years and a subsequent decline (P < 0.001). DCP presented a similar trend in the first 2 years (P < 0.01) but not at the following time points, whereas CC FDs constantly increased over time (P < 0.01). The best-fitted model for the microvascular parameters demonstrated that the main factors affecting SCP included time (P < 0.001), duration of diabetes (P = 0.007), and HbA1c (P = 0.03), whereas the DCP was influenced by LDi modifications (P = 0.006). The LDi and HPi were mainly influenced by SCP and CC perfusion in the parafovea (P = 0.02).
Conclusions: This study demonstrated an initial vasodilatory phenomenon resulting from a compensatory mechanism from the superficial vasculature, followed by capillary dropout. Initially, it would seem that there was an adaptive response by the DCP to the needs of the photoreceptors. Although the SCP may initially support the DCP, when the microvascular damage becomes diffuse and involves the SCP and CC it directly affects photoreceptor integrity.