High-Intensity Focused Ultrasound Circular Cyclocoagulation in Glaucoma: A Step Forward for Cyclodestruction?

Abstract

The ciliary body ablation is still considered as a last resort treatment to reduce the intraocular pressure (IOP) in uncontrolled glaucoma. Several ablation techniques have been proposed over the years, all presenting a high rate of complications, nonselectivity for the target organ, and unpredictable dose-effect relationship. These drawbacks limited the application of cyclodestructive procedures almost exclusively to refractory glaucoma. High-intensity focused ultrasound (HIFU), proposed in the early 1980s and later abandoned because of the complexity and side effects of the procedure, was recently reconsidered in a new approach to destroy the ciliary body. Ultrasound circular cyclocoagulation (UC3), by using miniaturized transducers embedded in a dedicated circular-shaped device, permits to selectively treat the ciliary body in a one-step, computer-assisted, and non-operator-dependent procedure. UC3 shows a high level of safety along with a predictable and sustained IOP reduction in patients with refractory glaucoma. Because of this, the indication of UC3 was recently extended also to naïve-to-surgery patients, thus reconsidering the role and timing of ciliary body ablation in the surgical management of glaucoma. This article provides a review of the most used cycloablative techniques with particular attention to UC3, summarizing the current knowledge about this procedure and future possible developments.

Figures

Figure 1

UCCC procedure. HIFU device (new-generation probe) comprises two elements: the probe with the six piezoelectric transducers generating the ultrasound beam and the coupling cone (a). The correctly positioned cone must show a homogeneous ring of visible sclera; when this ring is regular, the cone is then maintained by a mild vacuum system (b). After verification of the effective suction, the probe is inserted and stabilized into the cone (c). During the procedure, the cone is continuously filled with saline solution (d), in order to allow the ultrasound transmission. The treatment starts in the superior sectors with a progressive activation of each transducer (e).

Figure 2

Anterior segment-optical coherence tomography of the sclera before insonification. Preoperative normal sclera presenting a relatively homogeneous stroma, with some scattered linear- (asterisk) or oval- (arrowhead) shaped hyporeflective spaces interspersed between the collagen fibres.

Figure 3

Anterior segment optical coherence tomography of scleral modifications after successful UCCC. (a–c) Second-generation probes (8-second treatment; 4 mm wide active area); (d–f) first-generation probes (6-second treatment; 2.5 mm wide active area). Intrascleral hyporeflective spaces (arrows and asterisks), with a different degree of internal reflectivity, are clearly recognizable within the stroma. These spaces are prominent after seven days from the treatment (a), and persist, even though reduced, after one (b) and three (c) months. No significant macroscopic differences are detectable between the two generation probes, even though the current probes seem to induce a greater scleral delamination. Scans were taken at the superior-temporal quadrants, 3 mm from the site of previous filtration surgery.

Figure 4

The image shows an ocular surface thermogram obtained with a digital infrared camera, of a representative patient during 6-second dose insonification, immediately after removal of the 6 o'clock hour transducer. A single evident circular red spot is well distinguishable (arrowheads), which corresponds to an area of increased temperature at the site of transducer. Asterisk indicates the nose of the patient.

Figure 5

In vivo confocal microscopy of the superior temporal conjunctiva in the same patient scheduled to undergo a 4-second dose UCCC (Group 1). (a) The baseline planar reconstruction shows small roundish microcysts, located at different levels within the epithelium, scattered, and sometimes clustered (arrowhead). (b) Microcysts increased density and area (arrow) thirty days after insonification. Bar represents 100 μm (from [88], with permission of the publisher).

Figure 6

In vivo confocal microscopy of the superior temporal conjunctiva in the same patient scheduled to undergo a 6-second dose UCCC. (a) The baseline planar reconstruction shows features similar to those observed in Group 1. Somewhere, microcysts appear encapsulated (arrowhead) and filled with amorphous material or punctate reflective elements (asterisk). (b) Epithelial microcysts increased density and, especially, area (arrow) thirty days after UCCC. Microcysts may appear filled with amorphous material (black arrowhead) or reflective elements, probably representing inflammatory cells (arrows). Bar represents 100 μm (from [88], with permission of the publisher).