Histologic effects of a new device for high-intensity focused ultrasound cyclocoagulation

To evaluate the histologic effects and clinical outcomes of high-intensity focused ultrasound (HIFU) delivered by miniaturized annular transducers for ciliary body coagulation in an animal study.

Eighteen eyes of 18 rabbits were insonified with a ring comprising a six-sector transducer, to produce a 12.8-mm-diameter circular lesion. Six sectors were activated in six rabbits (group 1), five sectors in six rabbits (group 2), and four sectors in six rabbits (group 3) at 2 W acoustic power. The rabbits were examined before treatment (day 0) and after treatment on days 1, 7, 15, 21, and 28. Detailed qualitative and semiquantitative histopathologic analyses of the enucleated eyes were performed.

In the treated eyes, intraocular pressure changes ranged from -16.6 mm Hg (-55.3%) at day 28 to -8.9 mm Hg (-29.7%) at day 7 in group 1, from -4.7 mm Hg (-25.5%) at day 28 to -1.4 mm Hg (-7.6%) at day 21 in group 2 and from -7.9 mm Hg (-28.1%) at day 28 to +2.0 mm Hg (+7.1%) at day 7 in group 3. No macroscopic abnormalities were observed in the anterior segment or fundus. Histologic examination showed segmental-to-annular lesions in the ciliary processes, caused mainly by coagulation necrosis, whereas the sclera and lens appeared undamaged. Inflammation was very limited.

Ultrasonic coagulation of the ciliary body with HIFU delivered via a circular miniaturized transducer seemed to be an effective and well-tolerated method of reducing intraocular pressure in an animal study.