RESUMO
BACKGROUND: The purpose of the present study was to determine the effects of pars plana vitrectomy on retrobulbar haemodynamics in patients with proliferative diabetic retinopathy (PDR). METHODS: Colour Doppler imaging was used for measurement of blood flow velocities and resistive index of the ophthalmic artery (OA), posterior ciliary arteries (PCA) and central retinal artery (CRA) in 14 eyes of 14 patients with PDR before pars plana vitrectomy and at the 1 and 6 months after operation. The patients were also treated by laser photocoagulation before or during surgery. Twenty age- and sex-matched healthy subjects were used as control group. RESULTS: Mean peak systolic velocity and the end diastolic velocity of the CRA in the patients with PDR were lower and the mean resistive index was higher than in those of the control group (P < 0.05). The mean end diastolic velocity of OA in the patients was lower and the mean resistive index was higher than in the control group (P < 0.05). The peak systolic velocity of the OA and the end diastolic velocity of the CRA were significantly increased (P = 0.043 and P = 0.018, respectively) and the mean resistive index of the CRA was significantly decreased after pars plana vitrectomy (P = 0.043). No significant changes were detected among preoperative and postoperative values of peak systolic velocity, end diastolic velocity, and resistive index of the PCA and the mean velocity of the central retinal vein (P > 0.05). CONCLUSIONS: The blood flow velocities of OA and CRA are decreased but the resistive index is increased significantly in patients with PDR. Pars plana vitrectomy in patients with PDR may decrease resistive index and improve blood flow in the CRA.
