Short- and long-term effects on the ciliary body and the aqueous outflow pathways of high-intensity focused ultrasound cyclocoagulation.

Several physical methods can be used to coagulate the ciliary body and decrease intra-ocular pressure in patients with glaucoma. The study described here investigated the short- and long-term effects of high-intensity focused ultrasound (HIFU) cyclocoagulation on the aqueous humor production structures and outflow pathways. Thirty-four rabbit eyes were sonicated with a ring-shaped probe containing six miniaturized HIFU transducers. Light, scanning electron and transmission electron microscopy and corrosion casts were performed. In the affected regions, the epithelium of the ciliary processes was degenerated or necrotic and sloughed off. Examinations performed several months afterward revealed involution of the ciliary processes. Vascular corrosion cast revealed focal interruption of the ciliary body microvasculature. In most animals, a sustained fluid space was seen between the sclera, the ciliary body and the choroid, likely indicating an increase in the aqueous outflow by the uveoscleral pathway. These results suggest that HIFU cyclocoagulation has a dual effect on aqueous humor dynamics.

Miniaturized high-intensity focused ultrasound device in patients with glaucoma: a clinical pilot study.

PURPOSE: To evaluate the relative safety and potential efficacy of high-intensity focused ultrasound cyclocoagulation by a miniaturized annular device containing six piezoceramic transducers in patients with refractory glaucoma. METHODS: This was a three-center prospective interventional pilot study. Twelve eyes of 12 patients with refractory glaucoma were insonified using a ring-shaped probe containing six miniaturized high-frequency transducers operating at 21 MHz. Ultrasound biomicroscopy (UBM) and a complete ophthalmic examination were performed before the procedure and at 1 day, 1 week, 1 month, and 3 months after the procedure. Additional visits were performed 6 and 12 months after the procedure. RESULTS: Intraocular pressure was significantly reduced (P < 0.01) from a mean preoperative value of 37.9 ± 10.7 mm Hg to a mean postoperative value of 27.3 ± 12.4, 25.2 ± 11.3, 25.2 ± 7.7, 24.8 ± 9.8, and 26.3 ± 5.1 mm Hg at 1 day, 1 week, 1 month, 3 months, and 6 months, respectively, and to a mean value of 24.7 ± 8.5 at the last follow-up visit. No major intraoperative or postoperative complications occurred. Minor postoperative corneal complications developed in four patients with previous corneal abnormalities: superficial punctate keratitis (n = 3) and central superficial corneal ulceration (n = 1). UBM showed cystic involution of the ciliary body in 9 of the 12 eyes and a suprachoroidal fluid space in 8 of the 12 eyes. CONCLUSIONS: Ultrasonic circular cyclocoagulation using high-intensity focused ultrasound delivered by a circular miniaturized device containing six piezoceramic transducers seems to be an effective and well-tolerated method to reduce intraocular pressure in patients with refractory glaucoma.

Development of a miniaturized HIFU device for glaucoma treatment with conformal coagulation of the ciliary bodies.

This study examined the feasibility of high-intensity focused ultrasound (HIFU) for glaucoma treatment with conformal coagulation of the ciliary bodies (CB). A miniaturized high frequency (21 MHz) device was developed, based on the geometry of the eye and adapted to the anatomy of the rabbit eyeball. Six line-focus lesions were distributed along a circle and produced by six cylindrical transducers. To be conformal, the numerical model predicted an intensity of 6.9 W/cm(2), with exposure duration of 3 s ON (powered per sector). In vivo experiments were conducted on two rabbits. A significant intraocular pressure reduction was noted (-45% and -31%). Histology demonstrated conformal and homogeneous coagulation of the CB without side effects.

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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.