Dexamethasone has proven void of toxic effects when 0.1 ml was injected into the vitreous of rabbits in doses up to 400μg. Within three hours after injection half the original dose was cleared from the vitreous. Residual concentrations (0.05μg/ml) remained for at least four days. Experimentally induced Pseudomonas endophthalmitis could be adequately treated when a combination of dexamethasone (360μg) and gentamicin sulfate (500μg) was injected intravitreally within five hours of inoculation. In eyes treated with dexamethasone and gentamicin, a significant reduction of the inflammatory response in the anterior and posterior chambers, vitreous, retina and choroid occurred as compared to eyes treated with gentamicin alone. However, when treatment was started ten hours after infection, the inflammatory reaction was so severe that the retina was destroyed even though the infection was controlled.
Graham RO, Peyman GA. Intravitreal Injection of DexamethasoneTreatment of Experimentally Induced Endophthalmitis. Arch Ophthalmol. 1974;92(2):149-154. doi:10.1001/archopht.1974.01010010155016