Histologic effects of contact ultrasound for the treatment of glaucoma

The histologic effects of a contact ultrasound applicator were compared with those of the immersion applicator that is currently used clinically for the treatment of glaucoma. The applicator coupling cone uses a distensible rubber membrane that can be inflated to control stand-off distance relative to the surface of the eye. This feature allows the focal point of the therapeutic beam to be placed at selective depths. Histologic comparisons of lesions in rabbit and pig eyes showed lesions in the sclera and ciliary body that were similar to those produced by the immersion transducer when the same focal position was used. Moving the focal point to a greater depth resulted in less superficial damage, yet still produced ciliodestruction. Damage to the blood supply of the ciliary body, as found in human cadaver eyes, may be an additional mechanism of action of therapeutic ultrasound, and perhaps of other transscleral high-energy modalities.