Objectives: In the present study, we aimed to investigate the postural changes of systemic blood pressure, retrobulbar blood flow velocities, and intraocular pressure as a response to sildenafil. Material and methods: A total of 28 healthy volunteers with an average age of 51.4 ± 0.5 years (range: 46-53 years) were divided into two groups: study group (Group 1) and control group (Group 2). After baseline measurements of retrobulbar blood velocity in the ophthalmic, central retinal, and posterior ciliary arteries using color Doppler imaging and intraocular pressure were noted in both groups, sildenafil citrate (50 mg) was given to the participants in Group 1. All parameters were then re-measured in the sitting and supine positions. Mann-Whitney U test, Friedman variant analysis, and Wilcoxon two-related sample test were used to evaluate changes of these parameters with regard to position in both groups. Results: Changing from a sitting to a supine position decreased the systolic and diastolic blood pressures in both groups. These changes were not statistically significant between groups (p > 0.05). Intraocular pressure showed statistically insignificant increases in the supine position in both groups (p > 0.05). There were no statistically significant differences between the two groups with regard to the retrobulbar hemodynamic parameters in two (sitting and supine) positions (p > 0.05). Conclusion: This is the first clinical study on the effects of sildenafil on retrobulbar and systemic hemodynamics in postural variations. Retrobulbar hemodynamics, intraocular pressure, and systemic blood pressure are the same in patients who use recommended doses of sildenafil as in physiological conditions.