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A.S. Kwan, A. Ang, T.W. Isaacs, I.L. McAllister; Bacterial Contamination During Routine Pars Plana Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5536.
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Purpose: Endophthalmitis following routine vitrectomy is rare but has a severe ocular morbidity. There is no clear information on the likelihood of bacterial contamination during lengthy vitreoretinal procedure with a number of instrument manipulations. We investigate the occurrence of bacterial contamination during routine pars plana vitrectomy for non–endophthalmitis case and correlate the incidence of contamination with the total operating time and the total number of intravitreal instrument insertions. Methods: A prospective study was performed on 25 consecutive routine vitrectomies for non–endophthalmitis cases. No preoperative antibiotics were used. Preoperative (before the application of povidone–iodine) and postoperative conjunctival swabs were acquired. Two intraoperative vitreous aspirates were obtained from each case, one taken at the start and the other at the conclusion of the vitrectomy. The four specimens were cultured under aerobic and anaerobic conditions for 14 days. The total operating time was recorded and the total number of instrument insertions into the vitreal cavity for each case was meticulously counted. Results: The incidence of positive culture for preoperative conjunctival swab is 20%. There was no positive culture for vitreous aspirates obtained at the start of the operation. There was one case (4%) of positive culture for vitreous aspirates obtained at the end of the operation. There was one case (4%) of positive culture in the postoperative conjunctival swab which also had a positive culture in the preoperative conjunctival swab with the same organism, Escherichia Coli. The average length of the operations was 83±33 minutes and the average number of instrument insertions was 13±6 times. The length of the operation and the number of instrument insertions made no statistically difference to the incidence of positive culture. None of the culture positive cases developed endopthalmitis. Conclusions: The bacterial contamination rate of the vitreous during vitrectomy was extremely low. The conjunctiva is the likely primary source of bacteria. Povidone–iodine 5% at the start of the operation reduced the conjunctival bacterial load. Bacteria entered the eye during the vitrectomy does not necessarily cause endophthalmitis. Long operating time and large number of instrument insertions do not increase the incidence of bacterial contamination.
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