TIMING OF DEXAMETHASONE TREATMENT IN EXPERIMENTAL STAPHYLOCOCCUS-AUREUS ENDOPHTHALMITIS

Purpose: This study sought to determine whether intravitreal dexametha sone with vancomycin preserves retinal function in eyes with experimen tal Staphylococcus aureus endophthalmitis better than intravitreal van comycin alone. Methods: Twenty-four rabbits received intravitreal inje ctions in both eyes with S. aureus. Right eyes were treated with intra vitreal dexamethasone plus vancomycin and left eyes were treated with vancomycin alone at 24, 36, 48, or 72 hours after inoculation. Evaluat ion was performed by slit-lamp biomicroscopy, indirect ophthalmoscopy, and electroretinogram, Vitreous humor cultures and histopathologic ex aminations were performed on the eyes after the rabbits were killed. R esults: The combination of intravitreal dexamethasone and vancomycin r esulted in significantly less inflammation than vancomycin alone at 24 and 36 hours after inoculation, but electroretinograms showed signifi cantly better preservation only at 36 hours after bacterial inoculatio n. Viable bacteria were cultured from eyes treated 48 and 72 hours aft er inoculation. Conclusion: Intravitreal dexamethasone was found to be beneficial by electroretinography when administered 36 hours after in jection. In the authors' model, a single intravitreal injection of van comycin with or without the addition of dexamethasone was insufficient to sterilize eyes 48 and 72 hours after bacterial inoculation.