Microvascular abnormalities in dry eye patients

This study was conducted to evaluate conjunctival blood flow velocities and microvascular network density in patients with dry eye disease (DED). Twenty-five patients with DED and 25 healthy controls were recruited. The microvasculature and microcirculation of the temporal bulbar conjunctiva of the right eyes were assessed using a functional slit-lamp biomicroscope. Vascular variables included blood flow velocity (BFV), blood flow rate (BFR), microvascular network density and vessel diameter. A fractal analysis was performed using the box counting method to measure the fractal dimension (Dbox) representing the vessel density. The bulbar BFV was 0.59 ± 0.09 mm/s in the DED group and 0.47 ± 0.12 in the control group (P < 0.001). BFR was 169.5 ± 1.8 in the DED group compared to the control group (107.2 ± 49.6) (P < 0.001). Dbox was higher in DED patients (1.65 ± 0.04) than controls (1.60 ± 0.07, P < 0.05). Moreover, the vessel diameter was larger in the DED group (21.8 ± 1.8 μm) compared with controls (17.9 ± 2.2 μm, P < 0.001). Dbox was positively related with ocular surface disease index (OSDI) in patients with DED (r = 0.54, P = 0.008). Microvascular alterations were found in the bulbar conjunctiva of DED patients, including increased blood flow velocity, higher vessel density and larger vessel diameter.