Intravitreal steroid effect on intravitreal vancomycin clearance in rabbit eyes with pneumococcal endophthalmitis

Purpose. We showed previously that intravitreal steroid markedly reduces the blood-ocular barrier breakdown, inflammation, and tissue destruction associated with pneumococcal endophthalmitis (Vallar et al., ARVO Abstract, 1994; Park et al., Arch Ophthalmol,1995). We investigated whether intravitreal steroid therapy may also alter the rate of clearance of intravitreal vancomycin in these infected eyes. Methods. Albino rabbits were infected with an intravitreal inoculum of Streptococcus pneumoniae (2 × 10³ cfu). After 24 hrs, the rabbits were randomized to treatment with intravitreal vancomycin (1mg) alone or in combination with intravitreal dexamethasone (400 ug). The rabbits were euthanized 24 or 72 hrs following treatment. The infected eyes were enucleated and the vitreal concentrations of vancomycin were measured. Results. At 72 hrs following treatment, intravitreal vancomycin level was significantly higher in eyes treated with dexamethasone when compared to eyes not treated with dexamethasone (p < 0.05). No significant difference was noted between the two groups at 24 hrs following treatment. Conclusions. Intravitreal dexamethasone significantly reduces the rate of clearance of intravitreal vancomycin in rabbit eyes with pneumococcal endophthalmitis.