Intravitreal Dexamethasone Effect on Intravitreal Vancomycin Elimination in Endophthalmitis

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Abstract
STREPTOCOCCUS pneumoniae is a frequently encountered microorganism in endophthalmitis associated with a filtration bleb.1,2 Eyes with pneumococcal endophthalmitis generally have a poor outcome, despite prompt initiation of antimicrobial drug therapy, because of the destructive inflammatory response induced by the infection. In a previous study,3 we used a rabbit model of pneumococcal endophthalmitis to show that intravitreal dexamethasone therapy, when used in conjunction with intravitreal vancomycin administration, markedly reduced the inflammation and tissue destruction associated with the infection. A more recent study4 using a contrast-enhanced magnetic resonance imaging technique showed that intravitreal dexamethasone use also markedly reduced the associated blood-ocular barrier breakdown. Because the degree of breakdown correlates with the degree of intraocular accumulation of proteins and leukocytes from the blood,5-7 it is possible that a change in breakdown may affect the rate of elimination of a drug from the eye after intraocular administration. In this study, intravitreal vancomycin levels were measured in healthy eyes and in eyes with pneumococcal endophthalmitis to determine whether intravitreal dexamethasone therapy affects the elimination of vancomycin from the vitreous after intravitreal administration.