Effects of intravitreal corticosteroid in the treatment of Staphylococcus aureus-induced experimental endophthalmitis

PURPOSE: To investigate whether intravitreal injection of dexamethasone in addition to antibiotics can minimize intraocular tissue injury caused by Staphylococcus aureus endophthalmitis. METHODS: Albino rabbits were infected with an intravitreal injection of 1000 colony-forming units of S. aureus. The rabbits were randomized to receive no treatment (control group; n = 2), intravitreal vancomycin and amikacin (n = 5), or a combination of intravitreal vancomycin, amikacin, and dexamethasone (n = 5) 20 hours following inoculation of bacteria. All rabbits except for the control group also received intravenous imipenem every 8 hours for 4 days. The eyes were evaluated by clinical examination, electroretinogram (ERG), and histologic studies. RESULTS: Eyes treated with intravitreal dexamethasone demonstrated less inflammation on clinical examination compared with eyes that received antibiotics alone. The ERG responses of eyes that received both intravitreal antibiotics and steroid were significantly better at 45 hours, 7 and 14 days following inoculation (P < 0.05) compared to eyes that received antibiotics alone. Histologic studies 14 days following infection demonstrated less tissue destruction for eyes treated with dexamethasone. CONCLUSION: Compared to intravitreal antibiotics alone, intravitreal corticosteroids may improve visual outcome of S. aureus endophthalmitis by reducing inflammation and preserving electrophysiologic retinal function.