Nonpenetrating deep sclerectomy

www.expert-reviews.com ISSN 1746-9899 © 2009 Expert Reviews Ltd 10.1586/EOP.09.21 The goal of glaucoma filtration surgery is to reduce elevated intraocular pressure (IOP) in order to preserve residual viable elements of the optic nerve head. Trabeculectomy has been the ‘gold-standard’ filtration procedure for the last 40 years. In trabeculectomy, a full-thickness sclerostomy is created under a partial scleral flap. The aim of the scleral flap is to overcome the vast majority of complications associated with fullthickness filtration procedures by controlling the passage of aqueous from the anterior chamber (AC). This control mainly depends on the tightness of the scleral flap closure. However, frequent and serious intra operative, and early and late postoperative complications continue to occur, such as hyphema, cataract, vitreous loss, corneal endothelial cell loss, intraocular inflammation, suprachoroidal hemorrhage and bleb-related infections and overfiltration with its complications, including shallow or flat AC, hypotony, choroidal detachment and hypotony maculopathy [1–15]. Nonpenetrating glaucoma surgery aims to overcome most of the complications that are usually associated with full-thickness filtration surgery. It was first described by Epstein [16] and Krasnov [17] in the late 1950s and 1960s, respectively. They suggested deroofing Schlemm’s canal (SC) as a means to lower IOP. The popularity of this procedure was limited since its effect is only short term, owing to conjunctival scarring over the bare trabeculum. In addition, the trabeculectomy technique, introduced by Sugar in 1959 [18] and Cairns in 1968 [19], was easier to perform and had much longer long evity. Modifications of nonpenetrating glaucoma surgery in the early 1980s by Fyodorov et al. (deep sclerectomy [DS]) [20] and Zimmerman et al. (non penetrating trabeculectomy [NPT], in which a portion of the SC is excised under a superficial scleral flap) [21] has brought nonpenetrating glaucoma surgery back to the picture. Today, most of the performed nonpenetrating DS (NPDS) procedures combine the original DS and NPT, in which the floor of the SC and the juxtacanalicular meshwork are removed at the surgical site. Kozlov et al. in 1990 were the first to introduce a space-maintaining device in DS, using a highly purified collagen implant, and this was then followed by different, absorbable and nonabsorbable, expensive and low-cost implants [22]. Multiple studies have demonstrated the longterm beneficial effect of these devices on IOP reduction [23–33]; however, other studies failed to reveal such a benefit [34–36]. Saleh A Al Obeidan Department of Ophthalmology, College of Medicine, King Saud University, Airport Road, PO Box 245, Riyadh 11411, Saudi Arabia Tel.: +966 1477 5723 Fax: +966 1477 5724 [email protected] With the introduction of nonpenetrating deep sclerectomy (NPDS), the safety profile of filtering surgery has dramatically improved owing to the extraocular nature of the procedure that addresses abnormally increased aqueous outflow resistance in Schlemm’s canal and the juxtacanalicular trabecular meshwork without entering the anterior chamber. The use of spacemaintaining devices, antimetabolites and neodymium:YAG laser goniopuncture as adjuvant tools in NPDS has improved the long-term results, so that they are comparable with those of trabeculectomy. Therefore, NPDS has become the procedure of choice in the last few years for primary open-angle glaucoma, as well as some other forms of secondary open-angle glaucoma with surgeons who have mastered the procedure. NPDS involves removal of 4 × 4-mm deep scleral flap to deroof Schlemm’s canal and expose Descemet’s membrane, forming a decompression space or scleral lake. Aqueous humor reaches the scleral lake via the newly created trabeculo-Descemet’s membrane to be drained through different routes. The relatively long surgical learning curve remains the main disadvantage of NPDS. In this article, surgical technique, mechanism and routes of filtration, indications, contraindications, complications and results of NPDS will be discussed.