Porous polyethylene as a spacer graft in the treatment of lower eyelid retraction

Purpose: An experimental study was performed to: 1) assess the Tolerance an d incorporation of porous polyethylene (Medpor) in the posterior lamella of the rabbit lower eyelid; 2) analyze the effect of implant thickness on inc orporation; 3) investigate the ability of conjunctiva to grow over vascular ized Medpor and; 4) determine the effects of Medpor surface modification on biocompatibility and fibrovascularization. Methods: In phase I, 10 rabbit eyelids were operated on to analyze the effe cts of implant thickness and to develop the surgical technique used in phas e II of the study. In phase II, 20 lower eyelids of 10 rabbits received 0.8 5-mm-thick Medpor grafts, each rabbit receiving both an uncoated implant an d one coated with an immobilized collagen. Results: There were no extrusions in phase II. with a postoperative follow- up from 14 to 17 weeks. Fourteen of 20 eyelids had full-thickness conjuncti val incisions or excisions placed over the Medpor implant to determine the growth potential of conjunctiva over a vascularized implant. All but one ey elid showed complete defect coverage, occurring in as little as 3 days. His topathology indicated complete Medpor fibrovascularization as early as 4 we eks after implantation. Because neither coated nor uncoated implants extrud ed in phase II, no conclusions can be drawn regarding the efficacy of Medpo r surface modification. Conclusion: Medpor was well tolerated in this soft tissue application, and it offers advantages over other materials.