The long-term biocompatibility of porous Perfluoropolyether (PFPE) corneal inlays in humans

Abstract

Purpose: To evaluate long-term biocompatibility, optical clarity and the efficacy of Perfluoropolyether (PFPE) polymer as a corneal inlay in humans.

Materials and Methods: Corneas of 5 unsighted eyes of 5 patients received inlays: one patient selected as control. All were examined at baseline, immediately post-operative, 7 days and monthly thereafter for 12 months and at 3-monthly intervals for the next 12 months. Clinical evaluation includes detailed slit-lamp biomicroscopy, refraction, keratometry, corneal topography, and other routine ocular examinations.

Results: Surgery was uneventful. None of the patients developed corneal oedema or increased vascularisation during study period. All corneas were clear except for minimal haze around the edge of the implant and mild interface reflectivity. Two patients developed epithelial erosion with minimal stromal involvement at 4 and 24 months post surgery resulted in removal of inlay. Inlays remained stable in position in all patients, however clarity has reduced (4% - 26%) gradually with time. We believe mechanical stress from inlay to the surrounding tissue triggered keratocyte activation and extra cellular matrix material deposits around inlay may be responsible for epithelial erosions as well as the reduction in inlay clarity. All test eyes showed acute myopic shift by 8.47D ± 1.97 (mean ± SD) following implantation. The epithelial pigment deposits were detected in all test patients following surgery, related to acute corneal curvature changes. The removal data from two patients showed the reversal of the refractive effect to preoperative levels. One patient followed up for an extensive period of 19 months post inlay removal demonstrated stable results.

Conclusion: The PFPE inlays have demonstrated excellent biocompatibility within the human corneal tissue for 2 years. The epithelial erosion and inlay clarity reduction were the two major problems encountered in this study. We believe these problems were related to the mechanical stress induced tissue response from inlay. Critical patient selection and the modification of inlay design should improve the success of the procedure. Inlays are effective in altering the refractive status of the eye by altering the anterior corneal curvature. Also, inlay implantation and removal procedures are found to be easy, safe and quick without any complications.