Comparison of iodine compounds and levofloxacin as postoperative instillation; conjunctival bacterial flora and antimicrobial susceptibility following cataract surgery.

Purpose: To compare the cleanliness of the conjunctival sac following the use of iodine compounds (PAI) and levofloxacin as postoperative eye drops.

Study design: A prospective open-label study.

Patients and methods: Either topical levofloxacin or fourfold-diluted PAI was administered for 1 week postoperatively in 128 eyes of 128 patients who underwent routine cataract surgery. Conjunctival samples were obtained at three time points: pre-surgery, 1 week postoperatively, and 1 month postoperatively.

Results: The respective positive bacterial culture rates for postoperative iodine and levofloxacin were 88.1% and 85.2% pre-surgery, 71.6% and 50.8% 1 week postoperatively, and 92.5% and 86.5% 1 month postoperatively. Positive bacterial culture rates in both groups significantly declined at 1 week, and the rates returned to the baseline level 1 month postoperatively. The magnitude of reduction of DNA copy number detected by polymerase chain reaction at 1 week was larger in the levofloxacin group, although no significant differences were seen at pre-surgery or 1 month postoperatively. In the levofloxacin group, only one strain was culture positive at 1 week, however, its minimum inhibitory concentration (MIC) against S. epidermidis was high (128 µg/ml). The MIC value increased from 2.31 ± 2.19 µg/ml pre-surgery to 57.14 ± 22.34 µg/ml 1 month postoperatively, while no significant change was found in the iodine group.

Conclusion: Postoperative iodine and levofloxacin eye drops both reduced bacterial contamination in the conjunctival sac, with a superior level of disinfection in the levofloxacin group. However, postoperative levofloxacin eye drops enhanced the emergence of highly resistant bacteria, whereas no such development was seen in the iodine group.