Comparison of Conjunctival Flora Before and 12 Months After Dacryoendoscopic Recanalization for Lacrimal Passage Obstruction

<b>Background/Objectives</b>: To investigate the long-term changes in conjunctival bacterial flora before and after dacryoendoscopic recanalization for lacrimal passage obstruction using silicone tube intubation. <b>Methods</b>: This prospective study included 135 eyes with lacrimal passage obstruction that underwent lacrimal passage recanalization and were followed for at least one year. The silicone tubes inserted during surgery were removed three months postoperatively in all cases. The study period was from November 2018 to January 2025. Conjunctival samples were obtained before surgery and at 12 months postoperatively. Aerobic cultures were performed to detect bacterial flora. The culture positivity rate, number of bacterial species identified, and proportion of commensal bacteria were compared before and after surgery. <b>Results</b>: The bacterial culture positivity rate significantly decreased from 36.3% preoperatively to 20.0% postoperatively (<i>p</i> = 0.003). The number of bacterial species detected decreased from 15 to 6, with Gram-negative bacilli decreasing from 6 species to 1. In contrast, the proportion of commensal bacteria such as coagulase-negative staphylococci and <i>Corynebacterium</i> spp. relatively increased from 49.1% to 80.7%. No drug-resistant bacteria were detected postoperatively. <b>Conclusions</b>: Dacryoendoscopic recanalization for lacrimal passage obstruction was shown to achieve long-term normalization of the conjunctival bacterial flora by reducing pathogenic and drug-resistant bacteria and increasing commensal bacteria. These findings suggest that the procedure prior to intraocular surgery in patients with lacrimal obstruction may reduce the risk of postoperative infection.