Six-Month Preclinical Evaluation of a Bilayered ePTFE Glaucoma Implant in Normotensive Rabbits

Purpose: The efficacy of intraocular pressure (IOP)-lowering glaucoma surgery is limited by postoperative fibrosis. A bilayered expanded polytetrafluoroethylene (ePTFE) implant reduced fibrosis compared with silicone controls in a three-month study in normotensive rabbit eyes. Here, we evaluate biocompatibility and histopathology over six months. Methods: Twelve normotensive New Zealand white rabbits underwent bilayered ePTFE implantation in one eye and a sham procedure in the fellow eye. Clinical exams were monitored serially over six months and graded, including gross inspection, slit-lamp biomicroscopy, bleb evaluation, IOP measurement, and fundus examination. After six months, histopathologic analysis was performed on six eyes and graded for cellular integration, fibrosis, and inflammation. Results: The implant was well tolerated. No significant differences in conjunctival hyperemia or bleb vascularity were observed between implant and sham eyes; however, tube position was closer to the cornea at six months. In implanted eyes, IOP was reduced at postoperative day 1 (12.4 ± 1.6 mm Hg, P = 0.001), week 1 (12.7 ± 1.9 mm Hg, P = 0.006), week 2 (12.9 ± 2.0 mm Hg, P = 0.002), month 1 (13.1 ± 1.5 mm Hg, P = 0.01), and month 3 (14.1 ± 2.1 mm Hg, P = 0.04) versus baseline (16.5 ± 2.9 mm Hg). Sham eyes showed reductions at day 3 and week 2. Histopathology demonstrated cellular integration into the outer ePTFE layer, with minimal inflammation (0.9 ± 1) and fibrosis (1.1 ± 0.2). Conclusions: A bilayered ePTFE glaucoma implant was well tolerated for six months, with minimal inflammation or fibrosis. Translational Relevance: A low-profile, bilayered ePTFE implant is well tolerated and promotes tissue integration, supporting tissue-integrated filtration as a potentially more effective glaucoma surgery.