Trabeculectomy with internal tube shunt: a novel glaucoma surgery.

PURPOSE To describe a pilot study that evaluates the efficacy and mechanism of action of a new glaucoma operation, trabeculectomy with internal tube shunt. METHODS Twenty-three patients underwent the new operation in one eye for open angle glaucoma. Under a scleral flap, a deep sclerectomy was performed, resulting in an intrascleral lake. Laterally, on both sides, a small silicone tube was placed between the intrascleral lake and the suprachoroidal space. A trabeculectomy stoma and a peripheral iridectomy permitted easy access of aqueous to the tube. Postoperative and preoperative results were analyzed and also compared with results of 45 eyes that underwent a conventional trabeculectomy. RESULTS After a mean follow-up time of 324 days, the mean postoperative IOP was 13.8 mm Hg compared with a preoperative value of 25.4 mm Hg. The mean number of postoperative medications was only 1.1 compared with a preoperative value of 3.0. No significant change in outflow facility was seen. The bleb size was very small. In comparison, in conventional trabeculectomy eyes, the outflow facility and bleb size were significantly larger. CONCLUSION Trabeculectomy with internal tube shunt is very effective in lowering IOP. It is postulated to work, to a large extent, by allowing access of the aqueous humor to the suprachoroidal space where the protein colloid osmotic pressure of uveal blood causes its absorption. This new procedure offers many advantages over other filter procedures and tube shunts.