Surgical technique to prevent malposition of the Hydrus glaucoma microstent (The “gap sign”)

The key challenge of implanting the hydrus glaucoma microstent is avoiding the tip from exiting Schlemm's canal and diving posteriorly toward the iris root. Here, we propose a novel theory as to why the hydrus stent tends to dive posteriorly and we describe surgical steps to prevent this from occurring. These steps include making a corneal incision oriented tangential to the angle, having a flat angle of attack to Schlemm's canal, and relaxing the hand before advancing the stent. Observing a gap between the stent and the back wall of the hydrus injector ("gap sign") indicates that the stent is striking the back wall of Schlemm's canal and is likely to dive posteriorly unless the surgeon's hand position is adjusted.