Color-Doppler flow imaging: Examination technique, detectability and flow analysis of orbital vessels

We studied the main ocular and retrobulbar vessels with color-Doppler US and report on examination technique, detectability of the vessels and their flow characteristics to define the normal ranges of Doppler spectra for each artery and vein. We comparatively examined both eyes of 20 healthy subjects. Of each eye we studied the ophthalmic artery, the central retinal artery, the ciliary artery, the central retinal vein and the superior ophthalmic vein. The following flow parameters were considered: peak systolic velocity, end-diastolic velocity and resistive index for arteries; maximum and minumum velocity for veins. The examination lasted about 10 minutes per eye - 20 minutes for each subject. In all subjects the five investigated vessels were identified in both eyes, and adequate Doppler spectra were obtained. The average peak systolic velocities of ophthalmic, central retinal and ciliary arteries were respectively about 35, 12 and 10 cm/s, with low resistance patterns (resistive index: 0.75, 0.72 and 0.68, respectively). The venous flow, which is usually continuous, may be sometimes influenced by cardiac and respiratory activities: the maximum velocities of superior ophthalmic and central retinal veins were about 6 and 5 cm/s, respectively. Color-Doppler US noninvasively visualizes both ocular and retrobulbar vessels, providing major hemodynamic information from different flow parameters; the knowledge of these parameters in normal conditions can be the basis of hemodynamic studies in many abnormal orbital conditions.