Berger E.

Department of Ophthalmology, University of Rostock, Germany

Purpose: In the last few years keratoprosthesis research was focused on evaluating potential haptic materials that may promote better biointegration. Tissue adhesion and fibroblast ingrowth into the keratoprosthesis haptic are important factors to ensure a permanent fixation of the prosthetic device and to withstand trauma. In disease with opacity of the anterior part of the cornea lamellar keratoprosthesis could be suffizient and solve problems like retroprosthetic membranes.
Methods: Experiments were carried out with porous polydimethylsiloxane foam with a pore size ranging from 100 to 200 µm and a thickness of 200 µm and polytetrafluoroethylene with 63 to 78 µm pore size and 240 µm thickness. Biomaterial surfaces were modified by low pressure plasma treatment. Polymer samples were implanted in the corneal stroma of new zealand white-rabbits for a period of 8 weeks, half and one year. Biointegration in cornea, keratocytes ingrowth and collagen deposition were evaluated by histological methods.
Results: After implantation of porous polydimethylsiloxane foam and polytetrafluoroethylene neither acute nor chronic rejection were macroscopically seen. Histological examination showed no breakdown of the biomaterial up to one year but keratocytes ingrowth into the porous and tissue adhesion. The cornea around the implantation region was clear and no formation of a "second anterior chamber" was observed.
Conclusions: Polydimethylsiloxane foam modified by plasma treatment could be a promising haptic material with the advantage to allow a "true" chemical linkage in a keratoprosthesis, having the optical core of transparent silicone. Optimization of silicone foam as haptic material and in vivo evaluations of implanted keratoprosthesis still need further investigation.

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