Non Pentrating Glaucoma Surgery ( Deep Sclerectomy and Viscocanalostomy )
Nonpenetrating glaucoma surgeries have been developed in recent years in order to improve the safety of conventional filtering procedures. The goal of nonpenetrating filtering procedures is to reduce intraocular pressure by enhancing the natural aqueous outflow channels, while reducing outflow resistance located in the inner wall of the Schlemm’s canal and the juxtacanalicular trabecular meshwork. In the last few years viscocanalostomy and deep sclerectomy with external trabeculectomy have become the most popular nonpenetrating filtering procedures. Both involve removal of a deep scleral flap, the external wall of Schlemm’s canal and corneal stroma behind the anterior trabeculum and Descemet’s membrane, thus creating an intrascleral space. The aqueous humour leaves the anterior chamber through the intact trabeculo-Descemet’s membrane into the scleral space, from where it will egress into different pathways. The technique is associated with a long learning curve. Published clinical trials comparing nonpenetrating glaucoma surgery to full-thickness trabeculectomy have a consensus on the superior safety profile of nonpenetrating glaucoma surgery but are not in agreement when it comes to efficacy, where conflicting results have been found. This article reviews the nonpenetrating surgical techniques, mechanisms of action, indications, contraindications, complications, and results.
The aim of glaucoma surgery is to lower the intraocular pressure in order to reduce the risk of further glaucomatous progression, particularly in cases refractory to topical therapy. Although effective in reducing intraocular pressure, these procedures are not without complications, with endophthalmitis being one of the most serious. A PubMed review of the literature was performed for trabeculectomy, glaucoma drainage device procedures (Ahmed, Baerveldt and Molteno implants) and non-penetrating glaucoma surgery (deep sclerectomy and viscocanalostomy) for reports of postoperative infection, including blebitis and endophthalmitis. The literature on infections relating to non-penetrating glaucoma surgery is sparse compared with penetrating surgery, but this may be a reflection of the relatively shorter follow-up duration and comparatively smaller body of data available on non-penetrating procedures. Overall, there is not enough evidence, in terms of well-constructed randomised clinical trials with sufficiently large sample sizes and long follow-up durations, to be able to make informed comparisons of the risk of postoperative endophthalmitis and infection between the various glaucoma operations. This review article summarises the incidences of endophthalmitis from the literature and discusses the major risk factors for postoperative infection.
- PMID:19897472[PubMed – indexed for MEDLINE]
Video showing the technique of NPGS, using regular instruments. Difficulties like micro perforation, macro perforation and searching for the canal of Schlemm to de-roof is shown.
Non Pentrating Glaucoma Surgery : technique and difficulties.