Long-Term Intraocular Pressure-Lowering and Antifibrotic Effects of a Biodegradable HA-Mg Glaucoma Drainage Implant in a Chronic Glaucoma Rabbit Model.

Abstract

PURPOSE: The purpose of this study was to evaluate the long-term intraocular pressure (IOP)-lowering efficacy, antifibrotic activity, and outflow patency of a hydroxyapatite-coated degradable magnesium (HA-Mg) glaucoma drainage implant in a chronic glaucoma rabbit model. METHODS: Chronic glaucoma was induced by anterior chamber injection of a magnetic bead suspension, and glaucomatous damage was confirmed by retinal thinning and optic nerve injury. In a separate cohort, glaucomatous eyes were randomized to trabeculectomy (TL), sham surgery, or HA-Mg implantation (n = 6/group) and followed for 6 months. IOP and corneal diameter were monitored longitudinally, aqueous outflow was evaluated using intracameral trypan blue, and filtration tissues were examined histologically. RESULTS: Modeled eyes maintained IOP at approximately 30 millimeters of mercury (mm Hg) for 6 weeks, accompanied by retinal thinning and optic nerve damage. After treatment, IOP in the HA-Mg group decreased below 21 mm Hg and remained significantly lower than in the sham and TL groups, in which IOP remained elevated or rebounded. Only HA-Mg-implanted eyes showed recovery of corneal diameter to baseline at 6 months. Trypan blue testing demonstrated persistent subconjunctival drainage in the HA-Mg group, and histology revealed reduced fibroblast proliferation, decreased collagen deposition, and preservation of a clear filtration pathway. CONCLUSIONS: The degradable HA-Mg implant was well tolerated, provided sustained IOP reduction, and maintained outflow patency while attenuating postoperative fibrosis, supporting its potential for clinical translation in glaucoma filtration surgery. TRANSLATIONAL RELEVANCE: A biodegradable HA-Mg drainage implant that sustains outflow and limits fibrosis may offer a safer and more durable alternative to permanent subconjunctival drainage devices.