Abstract
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 x 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.