In Vivo Evaluation of Preoperative Topical Strategies in Reducing Conjunctival Microbial Load before Intravitreal...

To evaluate in vivo efficacy of different topical strategies administered before intravitreal injections (IVIs) in reducing conjunctival microbial load compared with standard preoperative disinfection with 5% povidone-iodine (PI-5%).

This prospective randomized comparative study was conducted between January and July 2025 at a tertiary referral ophthalmology center. Patients scheduled for IVIs were randomly assigned to 4 groups: 0.1% Polyquaternium-133, 0.6% povidone-iodine, 0.02% chlorhexidine digluconate, or no preoperative drops [control group (CG)]. Antiseptic eye drops were administered 3 times daily for 3 days before the procedure. Conjunctival swabs were collected at baseline (T0), on the day of injection before standard disinfection (T1), and 3 minutes after PI-5% application (T2). Microbial load was assessed by colony-forming unit (CFU) count, and microorganisms were identified.

A total of 205 patients were enrolled. In the CG, no significant difference was observed between T0 and T1, while PI-5% produced a significant CFU reduction at T2. Preoperative treatment with 0.6% povidone-iodine or 0.02% chlorhexidine digluconate did not significantly reduce CFU counts at T1. In contrast, 0.1% Polyquaternium-133 resulted in a significant reduction in bacterial load between T0 and T1, with a further decrease after PI-5%. Qualitative analysis showed selective effects of antiseptics on conjunctival microbial composition, with Polyquaternium-133 demonstrating marked activity against predominant species, including Corynebacterium macginleyi and Staphylococcus aureus.

Complete conjunctival sterility was not achieved with any regimen. However, 0.1% Polyquaternium-133 significantly reduced conjunctival bacterial load and showed a complementary effect when combined with standard PI-5% disinfection, suggesting potential clinical benefit in prophylaxis.