Concave trabeculo-Descemet's membrane as an early sign of viscocanalostomy failure

Outcomes of Nd: YAG Goniopuncture After Viscocanalostomy/Phacoviscocanalostomy

PURPOSE

The aim of this study is to evaluate the safety and efficacy of laser goniopuncture (LGP) to lower intraocular pressure (IOP) post-viscocanalostomy (VC)/phacoviscocanalostomy (PVC). Outcomes include: IOP reduction from pre-LGP levels and the need for further topical antiglaucomatous medication or surgery.

PATIENTS AND METHODS

A total of 541 eyes that underwent VC/PVC between 2009 and 2012, at the Stanley eye unit in Abergele were included in the study.

INCLUSION CRITERIA

All patients who had LGP at any timepoint after VC/PVC when target IOP was not achieved +/- progression in visual field with at least 6 months of follow-up data.Statistical analysis was performed on IOP values pre- and post-LGP, involving χ, Fischer exact, Mann-Whitney U, and Wilcoxon tests. A P-value of <0.05 was accepted as the level of significance.

RESULTS

Of the 515 included eyes, 136 (26%) required LGP after a mean of 15.11±9.73 months after surgery (95% confidence interval, 13.46-16.76 mo), ranging from 1 to 42 months. LGP reduced IOP significantly from a mean of 22.92±5.80 to 17.08±5.30 mm Hg immediately for all eyes, a reduction of 5.84 mm Hg (or a 25% reduction) (P<0.0001). IOP significantly reduced in the VC group with a mean reduction of 7.60 mm Hg compared with 4.85 mm Hg in the PVC group immediately after the procedure (P=0.0038). LGP was required sooner in the VC group compared with PVC, 11.35 and 14.57 months, respectively (P=0.0393). A total of 69 (62%) eyes were commenced on topical IOP-lowering medications, mean 7.26±6.41 months after LGP.

CONCLUSIONS

This study supports previous evidence that LGP enhances the IOP-lowering success of VC/PVC. The advantages of LGP are that it is a minimally invasive clinic-based procedure with a low complication rate.

Nonpenetrating glaucoma surgery

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.