Recently it has been demonstrated that retinal hemodynamics are disturbed in patients with chronic open-angle glaucoma. As the underlying cause a reduction in perfusion pressure due to increased intraocular pressure (IOP) and deficiencies of retinal autoregulation has been discussed. The present study was undertaken to clarify the influence of filtering surgery on retinal hemodynamics in patients with chronic open-angle glaucoma. A total of 17 patients with chronic open-angle glaucoma aged between 37 and 86 years were included in this prospective study. All patients underwent digital fluorescein angiography before and 10 days after fistulating procedures. From the angiograms the arteriovenous passage time (AVP) and arterial mean dye-bolus velocity (MDV) were quantified by means of digital picture analysis. At baseline the AVP was significantly prolonged in the patients as compared with reference values (AVP, 2.5 +/- 0.8 versus 1.6 +/- 0.4 s; P < 0.01). After the fistulating procedure (IOP: before, 29 +/- 5 mmHg; after, 16 +/- 4 mmHg) the AVP was significantly reduced as compared with baseline values (AVP, 2.5 +/- 0.8 versus 2.0 +/- 0.4 s; P < 0.05), whereas the MDV showed only a slight increase (MDV, 5.70 +/- 0.89 versus 5.99 +/- 0.92 mm/s; P > 0.05). This study confirms a disturbance of retinal hemodynamics in patients with chronic open-angle glaucoma. The significant reduction in AVP observed after lowering of the IOP by fistulating procedures demonstrates the positive influence of IOP reduction on the retinal circulation. The improvement in retinal circulation may prevent the occurrence of further glaucomatous damage after fistulating procedures.