Deep Sclerectomy

Abstract

Filtering surgery evolved from the classic trabeculectomy, in which penetration into the anterior chamber is a necessary step, toward nonpenetrating deep sclerectomy. The first procedure presents several serious complications, such as durable hypotony, hyphema, flat anterior chamber, choroidal detachment, endophthalmitis, and surgery-induced cataract. To avoid such drawbacks, a novel nonpenetrating technique was designed to improve the predictability of the intraocular pressure (IOP)-lowering action, while reducing the incidence of the immediate postoperative complications encountered with the penetrating method. This surgery works by building up new outflow pathways for the drainage of the aqueous humor while maintaining the integrity of the anterior chamber. Deep sclerectomy acts at the bulk of main resistance to aqueous humor egress, located at the juxtacanalicular meshwork and at the inner wall of Schlemm's canal. It consists of dissection of these two structures while keeping a thin filtering membrane through which aqueous humor is drained. The membrane prevents overfiltration and ensures a reproducible postoperative IOP. This surgery is indicated for most glaucomas, with the exception of angle closure and neovascular cases. The procedure consists in opening the conjunctiva and Tenon's capsule and creating a 5 × 5-mm limbus-based superficial scleral flap. A deeper scleral flap measuring about 4 × 4 mm is dissected and the roof of Schlemm's canal is removed. A space maintainer is inserted and the flap and conjunctiva are closed. Results after 10 years are good, with an IOP of 12.2 ± 4.7 mmHg and an overall success rate of 77.6% with few complications.