In Silico Comparison Of Hydrus® And Istent Inject® Microstents Across Patterns Of Schlemm’S Canal Collapse

To use a physiologically realistic in‑silico aqueous outflow model to compare the predicted intraocular pressure (IOP)–lowering performance of the Hydrus® and iStent inject® microstents across varying patterns of Schlemm’s canal (SC) collapse, with particular focus on differences in canal scaffolding, access to collector channels, and sensitivity to implantation location and orientation.

Computational (in‑silico) modeling study relevant to glaucoma and anterior segment evaluation, simulating glaucomatous eyes with heterogeneous and regionally collapsed Schlemm’s canal.

A previously described in‑silico framework for aqueous humor outflow was used to simulate eyes with no SC collapse, narrowing, and extensive collapse involving the implantation region. The Hydrus® microstent was modeled as a canal‑scaffolding device that enlarges a collapsed SC segment and spans multiple potential collector channel openings. The iStent inject® was modeled as a focal trans‑trabecular stent that pierces into SC at a single location without enlarging the canal. For iStent inject®, ideal placement near patent SC regions and adjacent collector channels was compared with representative placement deviations, including off‑axis orientation and lateral offset, reflecting limited intraoperative visualization of distal outflow.

Increasing SC collapse led to higher predicted IOP in the absence of a microstent. Hydrus® consistently produced robust IOP reduction across collapse patterns, maintaining efficacy even when the implantation region was severely collapsed. In contrast, iStent inject® demonstrated greater variability: strong IOP reduction was observed only when the device was well aligned with an open SC region near a collector channel, whereas modest deviations in location or orientation substantially reduced predicted efficacy, particularly in extensively collapsed canals.

In‑silico modeling suggests that Hydrus® functions not only as a bypass but also as a canal‑scaffolding device, reopening collapsed Schlemm’s canal segments and providing access to multiple collector channel openings without requiring precise focal placement. By contrast, iStent inject® does not enlarge the canal and relies on accurate placement at a favorable, and often poorly visualized, outflow location. These mechanistic differences may help explain variable clinical outcomes and support the use of anatomy‑aware modeling to inform device selection and surgical strategy in MIGS procedures.