SYNTHETIC HYDROGEL AS AN ARTIFICIAL VITREOUS BODY - A ONE-YEAR ANIMALSTUDY OF ITS EFFECTS ON THE RETINA

A hydrogel with a high water content was assessed in vitro and in vivo as a possible vitreous substitute. From a large series of polymers pr oduced by the aqueous polymerization of methyl acrylamidoglycolate met hyl ether (MAGME), a gel synthesized in 80% water was selected for an animal study. The gel was injected intravitreally into rabbit eyes and followed clinically by ophthalmoscopy, tonometry, and fundus photogra phy. The gel was clinically well tolerated, but after 6 months ophthal moscopy revealed progressive pallor of the optic nerve head. The eyes were enucleated one year after injection of polymer. Histopathological examination by light microscopy of retinal and vitreal sections revea led significant retinal disorganization, degeneration of the optic ner ve and retinal neural elements, retinal detachment, and inflammatory c hanges. Analysis of immunohistochemically labeled retinal sections rev ealed loss of ganglion cells and extensive pathological reaction of th e Muller cells and astrocytes. All these findings were consistent with a toxic effect of the polymer itself or some residual contaminants. T he cytotoxicity of the hydrogel was assessed in vitro using cultured m ouse (Balb/c-3T3) fibroblasts. The bioassay showed both cytostatic and cytocidal effects of the polymer. Our results indicate that hydrogels produced from MAGME monomer cannot function as vitreous substitutes b ecause of severe toxic reaction elicited to the posterior segment of t he eye.