Synthetic hydrogel as an artificial vitreous body: A one-year animal study 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 produced by the aqueous polymerization of methyl acrylamidoglycolate methyl 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 photography. The gel was clinically well tolerated, but after 6 months ophthalmoscopy 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 revealed significant retinal disorganization, degeneration of the optic nerve and retinal neural elements, retinal detachment, and inflammatory changes. Analysis of immunohistochemically labeled retinal sections revealed loss of ganglion cells and extensive pathological reaction of the Muller cells and astrocytes. All these findings were consistent with a toxic effect of the polymer itself or some residual contaminants. The cytotoxicity of the hydrogel was assessed in vitro using cultured mouse (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 because of severe toxic reaction elicited to the posterior segment of the eye.