To evaluate the color Doppler imaging (CDI) parameters of the retrobulbar circulation, we performed color Doppler imaging in both eyes of 29 glaucomatous patients with asymmetric cups [asymmetry >0.3 cup/disc ratio (C/D)] and asymmetric visual field loss. We used the QAD-1 Color Doppler unit (Quantum Medical Systems Inc.) with a 7.5-MHz linear-phased transducer to calculate the pulsatility index, and the peak systolic, end diastolic, and average blood-flow velocities in the ophthalmic, central retinal, nasal, and temporal short posterior ciliary arteries of each eye. In a second analysis, we compared the results of a randomly selected eye of age- and sex-matched controls. Paired t tests did not show any significant difference between the blood-flow velocities of the more damaged and less damaged eyes when the entire 29-patient group was considered together. The power was adequate to detect a 1.0 cm/s difference in most of the analyzed vessels. Thirteen of the 29 patients had primary open-angle glaucoma (POAG), and the remaining eyes had pseudoexfoliation and low tension, pigmentary, and chronic angle-closure glaucoma. When compared to age- and sex-matched controls, the less damaged eyes of patients with POAG displayed reduced systolic, diastolic, and mean velocities (p < 0.05) in the ophthalmic artery. In comparison, the more damaged eyes revealed statistically reduced velocities in the ophthalmic artery, temporal short posterior ciliary artery, and in all the parameters for the mean values of the short posterior ciliary arteries (p < 0.05). More advanced optic nerve damage in patients with POAG correlated with more severe reductions of CDI parameters of the retrobulbar circulation of patients with asymmetric disease. Further clinical color Doppler correlations are now mandatory to determine whether these vascular changes are pathogenetically important or epiphenomena.