Techniques and outcomes of minimally invasive trabecular ablation and bypass surgery

Abstract

Minimally invasive glaucoma surgeries (MIGS) can improve the conventional, pressure dependent outflow by bypassing or ablating the trabecular meshwork or create alternative drainage routes into the suprachoroidal or subconjunctival space. They have a highly favorable risk profile compared to penetrating surgeries and lower intraocular pressure with variable efficacy that may depend on the extent of outflow segments accessed. Since they are highly standardized procedures that use clear corneal incisions, they can elegantly be combined with cataract and refractive procedures to improve vision in the same session. There is a growing need for surgeons to become proficient in MIGS to address the increasing prevalence of glaucoma and cataracts in a well-informed, aging population. Techniques of visualization and instrumentation in an anatomically highly confined space with semi-transparent tissues are fundamentally different from other anterior segment surgeries and present even experienced surgeons with a substantial learning curve. Here, we provide practical tips and review techniques and outcomes of TM bypass and ablation MIGS.

Combined analysis of trabectome and phaco-trabectome outcomes by glaucoma severity

“…Ab interno trabeculectomy with the trabectome, a plasma surgical modality that ionizes and aspirates the trabecular meshwork with minimal energy transfer to surrounding tissues, was first introduced in 2004 4 and is considered a more mature microincisional glaucoma surgery. Trabectome surgery, similar to other surgeries in this family, has a favorable safety profile 5 but is often only performed in ocular hypertension or mild glaucoma stages 6 .…”

Rapid learning curve assessment in an ex vivo training system for microincisional glaucoma surgery

“…Microincisional glaucoma surgeries (MIGS) 1 primary open angle glaucomas to eyes that are relatively contraindicated, for instance after 52 failed trabeculectomy 6 or tube shunts, 7 in eyes with narrow angles, 8 and with peripheral 53 anterior synechiae. 6,9 54…”

Quantification of Focal Outflow Enhancement using Differential Canalograms

“…This approach may have limited use in vivo due to toxicity. 9 It is estimated that the smallest of the current trabecular meshwork microbypass implants is limited to drainage segments of about 608, 10,11 while larger ones access additional clock hours. 12 Trabecular meshwork ablation can provide more extensive angle access by allowing areas of discontinuity of the Schlemm's canal (SC) to be skipped (bypassed).…”

“…12 Trabecular meshwork ablation can provide more extensive angle access by allowing areas of discontinuity of the Schlemm's canal (SC) to be skipped (bypassed). 11,13 Although the trabecular meshwork is thought to be the anatomic location of primary outflow resistance, 14 intraocular pressures that are close to the theoretical limit of episcleral venous pressure 11 are rarely achieved with trabecular bypasses 15 or with trabecular ablation. 16 Here, we hypothesized that it is possible to develop a differential canalography technique to directly analyze areas of altered outflow before and after an intervention.…”

“…We refined recently introduced methods of quantitative canalography 17 and used them to measure conventional outflow enhancement following plasma-mediated ab interno trabeculectomy (AIT). We also present here the first animal model for AIT that provides tissues fresh enough to allow direct gonioscopic visualization 11 of the large, wedge-shaped TM. It guards outflow into the circumferential drainage segments of the characteristic angular aqueous plexus, 18 a structure that is relatively analogous to the Schlemm's canal in primates.…”