The Hydrus Micro-stent

Abstract

The Hydrus micro-stent (Ivantis, Irvine CA) is a novel Schlemm’s canal microinvasive glaucoma surgery (MIGS) device designed to enhance aqueous outflow into Schlemm’s canal and into the distal outflow veins. Made of flexible nitinol, an elastic nickel-titanium alloy, the device is designed to conform to the arc of Schlemm’s canal (Fig. 15.1). The proximal end is designed to provide a bypass inlet into the canal, with the main body of the implant designed to act as an intracanalicular scaffold which dilates the canal nine times its cross-sectional area for a length of 8mm or 3 clock hours in the eye. It has a non-luminal design to provide unimpeded access of aqueous to the collector channels and aqueous veins along the back wall of the canal, and three windows face the inner wall to stretch and increase the effective filtration area. The Hydrus thus is designed to address the underlying pathology in open-angle glaucoma – increased resistance in the inner wall and collapse of Schlemm’s canal – by creating a bypass through the inner wall and stretching the inner wall as well as scaffolding open the canal and preventing collapse (Figs. 15.2 and 15.3). The device is implanted using a handheld injector through a sub 2.0 mm clear cornea incision using a specially designed cannula to incise the inner wall to permit deployment of the device using a roller wheel (Fig. 15.4). Although the device may be implanted in any clock hour in the canal, it is most readily performed in the nasal quadrant using a temporal corneal incision. The device is currently an investigational device and an FDA pivotal trial is underway. There already have been a number of basic science and early clinical studies on the Hydrus device.