PreserFlo® MicroShunt: An Overview of This Minimally Invasive Device for Open-Angle Glaucoma

Abstract

For moderate-to-severe glaucoma, trabeculectomy remains the "gold standard" intraocular pressure (IOP)-lowering treatment; nonetheless, this method requires extensive post-operative maintenance. Microinvasive glaucoma surgery (MIGS) treatments are designed to lessen intra- and post-operative care burden while offering an acceptable IOP decrease for individuals with mild to moderate glaucoma. The PreserFlo^® MicroShunt (previously InnFocus MicroShunt) is an 8.5 mm glaucoma drainage device manufactured from poly(styrene-block-isobutylene-block-styrene) (SIBS), an extremely biocompatible and bioinert material. The lumen is narrow enough to prevent hypotony, but big enough to avoid being obstructed by sloughed cells or pigment. The device is implanted ab externo, as a stand-alone procedure or in conjunction with cataract surgery, with intraoperative mitomycin C, and a bleb is produced under the conjunctiva and Tenon's capsule. The MicroShunt was CE-marked in 2012 and designed for primary open-angle glaucoma, the IOP of which remains uncontrolled after maximally tolerated topical treatment. Several clinical trials evaluating the MicroShunt's long-term safety and effectiveness have been conducted, highlighting the effectiveness of the device over time, along with a tolerable safety profile. The present review aims to gather evidence of PreserFlo's effectiveness and safety results almost 10 years after its introduction, and furthermore, to compare it with other MIGS and with the gold-standard trabeculectomy for glaucoma management.

Keywords: InnFocus MicroShunt; MicroShunt; PreserFlo; PreserFlo MicroShunt; SIBS polymer; XEN Gel Stent; glaucoma; glaucoma drainage devices; micro-invasive glaucoma surgery; mitomycin C.

Figure 1

Simplified chemical structure of SIBS. M = number of isobutylene units; N = number of styrene units; SIBS = poly(styrene-block-isobutylene-block-styrene).

Figure 2

Anterior segment—optical coherence tomography (AS-OCT) showing successfully implanted PreserFlo MicroShunt, piercing the trabecular meshwork and positioned bevel up in the anterior chamber.

Figure 3

PreserFlo MicroShunt the day after surgical implant. Pretty visible tube in the anterior chamber, sutures over the conjunctiva and the forming filtering bleb.