Glaucoma is a disorder characterized by increased intraocular pressure. The aim of our study is to evaluate the hemodynamic changes in the eye before and after open angled glaucoma surgery, and to assess the importance of vascular events in the glaucoma surgery. 24 eyes of 24 patients with a mean age of 64.4 years were assessed before and after trabeculectomy in their 2nd and 10th weeks. Peak systolic velocity, end-diastolic velocity, mean average velocity, and resistive index (RI) values of ophthalmic, central retinal and short ciliary arteries were evaluated both before and after surgery with color Doppler ultrasonography and compared with Wilcoxon test. Statistically, RI value seemed to fall insignificantly, in ophthalmic artery whereas it increased significantly in central retinal artery, short temporal and nasal ciliary arteries. After the surgery, the fall in RI reflecting the capillary bed resistance, and increase in flow velocity values are thought to play role in the pathophysiology of open angled glaucoma.