Safety Profile of Minimally Invasive Glaucoma Surgery

Abstract and Introduction

Abstract

Purpose of Review: This article reviews the safety profile of trabecular meshwork/Schlemm's canal-based, subconjunctival, and suprachoroidal minimally invasive glaucoma surgery (MIGS).

Recent Findings: Prospective randomized clinical trials and metaanalyses published during the 2019–2020 review period provided important data regarding the safety profile of trabecular meshwork/Schlemm's canal-based MIGS. Transient hyphema and intraocular pressure spikes are among the most common complications associated with this category of MIGS, but more serious adverse events such as cyclodialysis cleft formation may also occur. Trabecular bypass microstents and the intracanalicular scaffold are further subject to device-related complications, including malposition and obstruction. Recent case reports and retrospective case series have further characterized the safety profile of the subconjunctival gel stent, with adverse events ranging from self-limited hypotony to visually devastating endophthalmitis and suprachoroidal hemorrhage. Five-year results of the COMPASS XT study demonstrated significantly greater endothelial cell loss in patients randomized to receive CyPass Micro-Stent (Alcon Laboratories, Fort Worth, TX, USA) in combination with cataract surgery versus those who underwent cataract surgery alone, and ultimately led to a Food and Drug Administration Class I recall of the device.

Summary: Trabecular meshwork/Schlemm's canal-based procedures are generally among the safest MIGS, with mostly self-limited and nonvision-threatening complications. Subconjunctival gel stent insertion is associated with both bleb-related and stent-specific adverse events, which are similar to those observed with trabeculectomy and tube shunt surgery, respectively. Removal of the CyPass Micro-Stent from the market underscores the need for high-quality, long-term safety data regarding MIGS.

Introduction

Minimally invasive glaucoma surgery (MIGS) has been defined by five features: an ab interno approach, minimal trauma to target tissue, at least modest efficacy, a favorable safety profile, and rapid recovery.^[1] The safety profile of MIGS is a potential advantage over traditional glaucoma surgery. Whereas vision-threatening complications have been well described with trabeculectomy and tube shunt surgery,^[2–4,5] MIGS are specifically designed to minimize such risks and allow for earlier surgical intervention in patients with milder glaucoma.

Numerous MIGS procedures targeting the trabecular meshwork/Schlemm's canal, subconjunctival space, and suprachoroidal space have become available during the past decade. Manipulation of each anatomical target involves unique risks. The widespread adoption of MIGS and availability of longer term follow-up data have added to our understanding of associated complications, some of which were not immediately evident in early clinical trials. Herein, we will review the safety profile of each subclass of MIGS (Table 1).

Table 1. Surgical complications in minimally invasive glaucoma surgery pivotal randomized clinical trials through two years of follow-up
Surgical complication	iStent [39,44] (n = 116)	iStent Inject [45] (n = 387)	Hydrus Microstent [51] (n = 369)	CyPass Micro-Stent [85] (n = 374)	Phaco [39,44,45, 51,85] (n = 553)*
Iritis	0.9%	5.7%	5.6%	8.6%	4.2%
Stent obstruction	4.3%	6.2%	3.8%	2.1%	Not applicable
Stent malposition	2.6%	Not reported	1.6%	0.5%	Not applicable
IOP ≥ 10 mmHg over baseline	4.3%	2.1%	0.5%	4.3%	3.1%
Conjunctivitis	0%	0.8%	5.7%	1.0%	4.5%
Persistent BCVA loss ≥ 2 lines	Not reported	2.6%	1.4%	1.6%	2.6%
Corneal edema	Not reported	Not reported	1.4%	3.5%	0.6%
Cystoid macular edema	0.9%	Not reported	2.2%	1.3%	1.6%
Hyphema	Not reported	Not reported	0.5%	2.7%	0.3%

BCVA, Best-corrected visual acuity; IOP, intraocular pressure; phaco, phacoemulsification.
*Total number of 'phaco' patients (n = 553) is pooled from the control groups in four pivotal randomized clinical trials evaluating iStent, iStent Inject, Hydrus t, and CyPass Micro-Stent.