Tissue interaction with hydrogel sponges implanted in the rabbit cornea.

We proposed poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel sponges as potential materials for the peripheral zone of a composite keratoprosthesis. It was previously shown that such sponges allowed cellular invasion when implanted s.c. in rabbits. To evaluate the reaction elicited by these materials in the corneal tissue, a PHEMA sponge, with pore size diameters of 10-30 microns, was produced, impregnated with collagen, and implanted in the rabbit cornea in both central and limbal regions of separate eyes. The eyes were examined by slit-lamp biomicroscopy up to 6 months postoperatively. Enucleation was performed at 3 weeks, 6 weeks, and 6 months, then excised implants were examined by light and transmission electron microscopy. Both clinical and histopathological examination indicated that sponges were well tolerated by the stromal and limbal tissues. No capsule was formed around any of the implants. Corneal fibroblasts and capillaries readily invaded the internal voids in the sponge to all depths. The invading cells remained viable and active up to the end of the follow-up period. Our findings suggest that hydrophilic PHEMA sponges may be successful as peripheral keratoprosthetic materials able to provide a permanent and tight fusion of the keratoprosthesis with the host tissue.