POLY(1-VINYL-2-PYRROLIDINONE) HYDROGELS AS VITREOUS SUBSTITUTES - HISTOPATHOLOGICAL EVALUATION IN THE ANIMAL EYE

A homopolymer of 1-vinyl-2 pyrrolidinone and its copolymer with 2-hydr oxyethyl methacrylate, both cross-linked with divinyl glycol, were pro duced as possible substitutes for the vitreous body of the eye. The hy drated polymers behaved like viscoelastic gels, displaying excellent p hysical and optical properties. The sterile gels (0.7-1.5 ml) were inj ected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exc eption of transient opacities in the vitreous. After 4 weeks, the oper ated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature i n all sections was the invasion of inflammatory cells. Vacuoles contai ning granular material, assumed to be polymer, were seen in the interc ellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It appeared that the biodegradati on of the internalized polymers did not proceed further, however, the fate of polymers and their usefulness as vitreous substitutes should b e investigated through long-term experiments.