OBJECTIVE To study the effect of antihypertensive drugs in essential hypertension and in the central retinal, posterior ciliary, and ophthalmic arteries by using Doppler sonography. METHODS Thirty patients with essential hypertension and 32 control subjects were enrolled in the study. The pulsatility and resistive indices were evaluated in the central retinal, posterior ciliary, and ophthalmic arteries before and 2 months after treatment with antihypertensive drugs as well as in the control group. The pulsatility and resistive index values for each artery in each group were compared statistically. RESULTS There were significant differences in the retrobulbar pulsatility and resistive index values in each artery among the patients with initially diagnosed hypertension and the control group (P < .05). There were significant reductions in the resistive and pulsatility index values of the posterior ciliary and ophthalmic arteries after treatment (P < .05). For the ophthalmic artery, posttreatment pulsatility and resistive index values did not reach the level of flow measured in the control subjects. CONCLUSIONS The alteration of Doppler parameters of medication-free patients with hypertension may result from a peripheral vasospasm in the retrobulbar circulation, and the improvement in the Doppler parameters with oral antihypertensive drugs may indicate the importance of early diagnosis in ameliorating hypertension-induced retrobulbar circulation changes.