COMPARATIVE TREATMENT OF BACTERIAL ENDOPHTHALMITIS

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The objective of this study is to establish a standardized animal model of bacterial endophthalmitis in the rabbit utilizing a gram positive coccus typically producing a mild disease (Staphylococcus epidermidis), a gram positive coccus typically producing a moderate clinical disease (Staphylococcus aureus), and a Ram negative rod which usually produces an overwhelming infection (Pseudomonas aeruginosa). The further objective of this study is to exploit this standardized model to determine the safest and most effective treatment regimen for the management of the disease. Intravenous antibiotics, intraocular antibiotics, pars plana vitrectomy and oral steroids will be tested in therapeutic combinations which mimic clinical practice. Studies will first be performed to demonstrate maximum vitreous levels produced in the inflamed eye by intravenous administration of antibiotic. Resistance of therapeutic levels of antibiotic in vitrectomized inflamed eyes after intraocular injection will also be measured. Time from inoculation of viable and heat-killed organisms at varying concentrations into the vitreous to the institution of therapy will be varied to simulate clinical settings. Comparison of therapeutic effects will be made on the basis of a quantitative scale for clinical signs by a masked observer, and evaluated for statistical significance by the t-test. Paired, concurrent control animals or the fellow eye of the same animal will serve as controls. Careful attention will be paid to the quantification of live vs dead bacteria in any experimental injection. Clinical outcome analysis will be augmented by evaluation of electroretinographic response, terminal vitreous cultures, and histopathologic evaluation by light and ultrastructural microscopy.