Impaired Autoregulation of Blood Flow at the Optic Nerve Head During Vitrectomy in Patients With Type 2 Diabetes

To determine whether type 2 diabetes mellitus (T2DM) influences autoregulation of optic nerve head (ONH) blood flow during vitrectomy. Cohort study. Thirteen eyes of 13 subjects with T2DM and 30 eyes of 30 controls without T2DM undergoing vitrectomy for epiretinal membrane or macular hole were included. Following 25 gauge vitrectomy, we measured the mean blur rate (MBR), an index of ONH blood flow, in the vascular area (vascular MBR) and in the tissue area (tissue MBR) using laser speckle flowgraphy. We performed measurements before and 5 and 10 minutes after intraocular pressure (IOP) elevation of approximately 15 mm Hg; both parameters represent relative values (%, compared with baseline). We calculated the vascular MBR recovery rate as (vascular MBR at 10 min–vascular MBR at 5 min)/(vascular MBR at baseline–vascular MBR at 5 min). Vascular MBR in T2DM subjects was significantly lower than that in controls at 5 and 10 minutes after IOP elevation (P = .0328 and P < .0001, respectively). Tissue MBR was also significantly lower in T2DM subjects than in controls at both time points (P = .0253 and P = .0004, respectively). Vascular MBR recovery rate was significantly lower in the T2DM than in the control group (P = .0090). Furthermore, the vascular MBR recovery rate was significantly negatively correlated with hemoglobin A1c and fasting plasma glucose levels (P = .0284 and P = .0381, respectively). T2DM is associated with impaired ONH blood flow autoregulation in both vascular and tissue areas when subjected to change in IOP during vitrectomy.