The aim of this study was to investigate the effects of sildenafil on ocular hemodynamics by color Doppler ultrasonography (CDU). In all, 38 patients with erectile dysfunction diagnosed by International Index of Erectile Function (IIEF) and Sexual Health Inventory of Men (SHIM) scores were included into the study. After taking 100 mg of oral sildenafil citrate, all patients underwent CDU examination of central retinal artery at 60 and 75 min and CDU examination of cavernosal artery at 20, 60 and 75 min. All of the side effects during and after the test were also recorded. The mean cavernous artery peak systolic flow velocity increased significantly after sildenafil. However, no significant change was determined in central retinal artery flow parameters including peak systolic flow velocity, end-diastolic flow velocity, resistive index, pulsatility index, volume and diameter. Five patients experienced ocular side effects. No significant change was observed in retinal artery CDU measurements of patients having ocular side effects. Sildenafil has no effect on ocular hemodynamics on the basis of CDU. Ocular side effects may be the result of other changes in retinal photoreceptors rather than the ocular circulation.