Temporal changes in ocular-surface bacterial contamination during cataract surgery and vitrectomy: effect of povidone–iodine

Postoperative endophthalmitis remains a serious complication of intraocular surgery, and reducing ocular-surface bacterial contamination is an important preventive strategy. We retrospectively evaluated temporal changes in ocular-surface/canthal irrigation-fluid culture positivity during cataract surgery and vitrectomy and its association with intraoperative povidone-iodine (PI) irrigation. Cases were divided into four groups according to additional PI use at cataract surgery onset (Phaco vs. Phaco-nPI) and repeated PI irrigation during vitrectomy (PPV vs. PPV-PI). Irrigation fluid samples were collected at the beginning of surgery in all groups and at the end of surgery in the Phaco, PPV, and PPV-PI groups. A total of 502 eyes were included (189 cataract surgeries and 313 vitrectomies). Initial cultures were positive in 12.3% of eyes overall across the Phaco, PPV, and PPV-PI groups, compared with 44.4% in the Phaco-nPI group. Culture positivity increased by final sampling only in the PPV group (13.1% to 33.8%; P < 0.001). Culture positivity showed a time-associated increase most consistently in the PPV group, with exploratory analyses suggesting a diminishing rate of increase during longer procedures; this pattern was not evident in the PPV-PI group, whereas the Phaco group did not show a consistent increase across statistical approaches. Coagulase-negative staphylococci, mainly Staphylococcus epidermidis, were the most common isolates, with no resistance to vancomycin or third-generation cephalosporins. Ocular-surface/canthal irrigation-fluid culture positivity persisted after disinfection and tended to increase during longer procedures; additional or repeated PI irrigation was associated with lower observed final-sample culture positivity, although residual PI carryover could not be excluded.