Experimental and clinical studies have confirmed the biocompatibility of keratoprostheses made of aluminum oxide ceramic (corundum). Poor results were obtained in cases where the prosthesis was exteriorized through the lid, leading to loosening and extrusion. An analysis of the problem indicated that the most likely cause is the continuous movement of the eye behind the lid. This resulted in constant stresses and shifts of interface between the plate and the adjoining tissues. Modifications in the size of the retaining plate or in the contour of the plate surface failed to improve the retention rate. We feel that improved stability of this implant can be obtained by reducing the diameter of the retaining plate while making modifications in the surgical technique to eliminate the shearing movements of the lid.