Effects Of Intensive Insulin Therapy On The Retinal Microvasculature In Patients With Type 2 Diabetes Mellitus: A Prospective Observational Study

Background: We examined the changes in retinal microvasculature in type 2 diabetes mellitus (T2DM) using optical coherence tomography angiography (OCTA) before and after intensive insulin therapy. Methods: : This prospective observational study recruited patients with T2DM and divided them into intensive insulin therapy and oral hypoglycaemic agent groups according to different hypoglycaemic methods. All patients enrolled in this study had diabetes without retinopathy or non-proliferative diabetic retinopathy. OCTA was used in all patients before treatment and at 1, 3, and 6 months after treatment. Changes of vessel density and thickness in the macular and optic disc areas were assessed. Results: : The study included 36 eyes in the intensive insulin therapy group and 36 eyes in the oral hypoglycaemic agent group. During the 6-month follow-up, the funduscopy findings of all patients were stable, without significant progression of retinopathy. One month after treatment, vessel density in the deep capillary plexus (DCP) and peripapillary capillary vessel density (ppVD) were significantly decreased by intensification ( P =0.009, 0.000). And, ppVD was significantly lower in the intensification group than in the oral agent group( P =0.000). At 3 months after treatment, decreases in vessel density induced by intensification were found in the superficial capillary plexus (SCP), DCP, foveal density in a 300-μm-wide region around the foveal avascular area (FD-300), and ppVD ( P =0.032, 0.000, 0.039, 0.000). The vessel densities of SCP, DCP, FD-300, and ppVD were significantly lower in the intensification group than that in the oral agent group ( P =0.002, 0.004, 0.039, 0.001). Six months after treatment, decreases in vessel density by intensification were observed in the DCP and ppVD groups ( P = 0.000, 0.000). The Vessel densities of DCP and ppVD in the intensification group were significantly lower than those in the oral agent group ( P = 0.004, 0.004). In the oral hypoglycaemic agent group, vessel density showed no significant change after treatment. Conclusions: : Insulin-intensive treatment caused a transient reduction in vessel density in both the macular and optic disc areas. Retinal microvasculature monitoring using OCTA is important for patients with type 2 diabetes receiving intensive insulin therapy.