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

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.

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.

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).

A bilayered ePTFE glaucoma implant was well tolerated for six months, with minimal inflammation or fibrosis.

A low-profile, bilayered ePTFE implant is well tolerated and promotes tissue integration, supporting tissue-integrated filtration as a potentially more effective glaucoma surgery.