Effect of pars plana vitrectomy on ocular hemodynamics and hydrodynamics
Purpose: To study the influence of pars plana vitrectomy (PPV) on ocular hemodynamics and hydrodynamics. Methods: Two groups (93 eyes) of patients were studied prospectively: (1) diabetic patients (47 eyes), who underwent PPV either because of vitreous hemorrhage or macular edema; (2) non-diabetic patients (46 eyes), operated for macular hole or epiretinal membrane. Linear flow velocity and bulk blood flow were measured in central retinal artery and ophthalmic artery with color Doppler imaging (Voluson 730Pro, General Electric). Blood Flow Analyzer was used to assess choroidal blood flow through measuring pulsate blood flow. Measurment of main parameters of hydrodynamics was performed with electric tonography before surgery and 2-12 months after surgery. Results: Indices of dopplerography and floumetry were consistent with each other and showed, on the one hand, deterioration of blood flow in Gentral retinal artery and posterior short ciliary arteries, and, on the other hand, improvement in blood circulation in ophthalmic artery as well as in posterior long ciliary arteries. Conclusions: It showed a post-vitrectomy redistribution of blood flow in favor of anterior segment of the eye (iris and ciliary body) that can be associated with high frequency of rubeosis iridis and anterior hyaloid fibrovascular proliferation in patients with diabetes mellitus during postoperative period. Though intraocular pressure was incresed in all patients after vitrectomy, most of them (66%) had intraocular pressure within the normal range and did not require treatment. However, 23% of patients required drugs lowering IOP for up to 1 month and 11% of patients required it for 6-12 months. During the observation period up to 2 years signs of glaucoma were not detected. Key words: hydrodynamics, hemodynamics, vitrectomy, intraocular pressure, rubeosis iridis