Laser trabeculodissection with a photopolishing scanning excimer laser.

A phase I study of nonpenetrating trabeculectomy (Zimmerman procedure) using a scanning excimer laser system was conducted to evaluate the ability of this laser system to achieve the deep dissection required to allow significant filtration without inadvertent penetration into the anterior chamber. A photopolishing, scanning 193 nm excimer laser system (LS 2000, LaserSight, Inc.) was used with a proprietary fluence, spot size, scanning pattern, and ablation shape to perform a trabeculodissection under a scleral flap with a limbal-based conjunctival flap in 8 cases of advanced glaucoma including 5 eyes that had a failed trabeculectomy. The laser trabeculodissection (LTD) was carried through Schlemm's canal and the juxtacanalicular trabecular meshwork, achieving vigorous aqueous outflow. No peripheral iridectomy was done. The scleral flap was closed loosely with a 10-0 suture. Mitomycin-C was used intraoperatively. In no case did inadvertent penetration into the anterior chamber occur. No peripheral iridectomy was performed. No intraoperative hyphema occurred. There was no postoperative iritis except minimal anterior chamber reaction in 1 eye with preoperative rubeosis. Postoperatively, a good filtering bleb was achieved in all 8 eyes with substantial reduction in the intraocular pressure without topical antiglaucoma therapy. No cases of postoperative shallowing (overfiltration) occurred. Gonioscopy, postoperatively, revealed no new peripheral anterior synechiae (PAS) to the filtration site and an intact inner trabecular meshwork. All eyes were followed for a minimum of 6 months. In this phase I study, laser trabeculodissection (LTD) with a 193 nm photopolishing, scanning system appears to be a promising alternative to full-thickness trabeculectomy, achieving significant filtration while perhaps avoiding much of the risk of filtration surgery. The laser system seemed to provide a more reliable, better-controlled dissection than a knife. The aqueous drainage seems to have acted as a self-regulating endpoint by absorbing UV energy, thus avoiding inadvertent penetration into the anterior chamber. More study is needed to establish the appropriate role of LTD in glaucoma therapy.