Insonation of the eye in the presence of microbubbles - Preliminary study of the duration and degree of vascular bioeffects - Work in progress

Objective. The purpose of this study was to investigate the presence and duration of vascular permeability changes induced by the combination of ultrasound and an intravascular microbubble contrast agent in the rabbit eye. Methods. Five eyes were studied in 8 anaesthetized rabbits. Insonation was performed with a diagnostic B-mode system (center frequency=2 MHz; mechanical index [MI]=0.2 and 1.7) for 5 minutes after administration of perflutren microbubbles (0.07 mL/kg). Fluorescein fundus angiography was performed before and 3 minutes after insonation; at 6 minutes, color fundus photography was used to assess the dye leakage, bleeding, and alteration of the diameter of fundus vessels. Results. Alteration of fundus vessel diameters was observed in I of 5 cases at a low MI and in 4 of 5 cases at a higher MI. In 1 case, leakage of fluorescein indicated increased permeability at the higher MI. No bleeding was detected in any case. Conclusions. The permeability change induced by insonation and this dose of an ultrasound contrast agent appears to be transient under the conditions studied, although the time delay between insonation and optical assessment limits the completeness of the findings. This preliminary study may be relevant to drug delivery strategies using ultrasound and microbubbles.