[Contamination of intraocular fluid in pars plana vitrectomy]

Endophthalmitis after pars plana vitrectomy is rare, with an incidence of 0.05-0.14%. The aim of this study was to evaluate the microbiological situation during pars plana vitrectomy and to ascertain what organisms and how many enter the eye during the operation.

Twenty-five consecutive subjects undergoing primary pars plana vitrectomy were included in the study. Patients were excluded if they had evidence of local or systemic infections or had undergone antibiotic therapy within 3 weeks before surgery. A standard three-port pars plana vitrectomy was performed on each patient. Preoperative smears of the conjunctiva and intraoperative aspirates of the vitreous were taken immediately after sclerotomy, and aspirates of the intraocular fluid at the conclusion of operation.

We obtained preoperative smears from the conjunctival sac of all patients, and found that 19 patients (76%) had positive cultures, with coagulase-negative staphylococci as the most commonly isolated organisms, (n = 14; 56%). Vitreous--aspirated immediately after sclerotomy--was sterile in 68% (n = 17). In 32% (n = 8) contamination occurred, the microorganisms isolated being coagulase-negative staphylococci (20%) and Staphylococcus aureus (12%). Five of the samples (20%) of intraocular fluid from the vitreous cavity--aspirated before wound closure--were contaminated, coagulase-negative staphylococci (8%) and Staphylococcus aureus (12%) again being found in culture. In no case did postoperative endophthalmitis develop.

This study demonstrates that bacteria enter the eye during pars plana vitrectomy and that there is a change in the contaminating bacterial species during operation. Even if bacteria remain in the eye after pars plana vitrectomy, postoperative endopthalamitis does not necessarily develop.