Vitrectomy in endophthalmitis. Results of study using vitrectomy, intraocular antibiotics, or a combination of both

A rabbit model of endophthalmitis was produced by inoculating Staphylococcus epidermidis and S aureus into the vitreous cavity. Elimination of microorganisms was compared using intravitreal administration of 0.1 mg of gentamicin alone, vitrectomy alone, and a combination of gentamicin and vitrectomy. In the case of S. epidermidis treated 24 hours after inoculation, all untreated eyes were culture-positive at one week, eyes treated with gentamicin alone or intravitreal gentamicin in combination with vitrectomy were all culture-negative, and vitrectomy alone rendered half of the eyes culture-negative. In the case of S aureus, eyes not treated by vitrectomy alone were all culture-positive at one week. Eyes treated with intravitreal gentamicin 25 to 31 hours after infection were culture-negative for S aireus in 33% at one week, while eyes treated with combined vitrectomy plus intraocular gentamicin were culture-negative in 83% of cases. When treatment was delayed 40 to 49 hours after inoculation of S aureus, intravitreal rendered 50% culture-negative at one week, while vitrectomy combined with intravitreal gentamicin eliminated the infection in 100% of eyes.