The most important problem in the transplantation of artificial cornea is the extrusion of keratoprosthesis. So we performed this study to know the conditions to keep the keratoprosthesis as long as possible after animal experiment with experimental keratoprosthesis of various material and structure. We concluded from the results that silicone barrier could not prevent the retroprosthetic membrane, and fluorosilicone was not adequate material as an optic. And the following conditions are required to maintain keratoprosthesis as long as possible; optic made of PMMA, retention plate made of PTFE with 0.6 mm thick, anterior direction of optic, large optic, intralamellar suture technique. Furthermore we postulated that enzymatic theory is more appropriate than aseptic necrosis theory about the extrusion of keratoprosthesis.