From Bench to Application: Evaluating the In Vitro and In Vivo Efficacy of a Polyhexamethylene Biguanide and Cross-Linked Hyaluronic Acid-Based Antiseptic Solution

<b>Background/Objectives</b>: In the context of increasing bacterial resistance and the need for effective ophthalmic antiseptics, this study evaluates the antimicrobial efficacy of Corneial MED^®, a novel ophthalmic solution containing polyhexamethylene biguanide (PHMB) and cross-linked hyaluronic acid. The study investigates the in vitro fungicidal and bactericidal properties of this solution against clinically relevant fungal and bacterial strains and its impact on conjunctival flora in vivo. <b>Methods</b>: The in vitro assessment included time-kill assays to determine the fungicidal or fungistatic activity against <i>Candida albicans</i>, <i>Aspergillus flavus</i>, and <i>Aspergillus fumigatus</i>. The bactericidal activity was evaluated against <i>Staphylococcus aureus</i> (methicillin-sensitive and -resistant), <i>Staphylococcus epidermidis</i>, <i>Pseudomonas aeruginosa</i>, and <i>Escherichia coli</i>. In vivo, 43 patients undergoing cataract surgery were treated with the solution for three days preoperatively. <b>Results</b>: Corneial MED^® demonstrated a fungistatic effect against <i>C. albicans</i> and <i>A. fumigatus</i>, while it exhibited limited activity against <i>A. flavus</i>. The tested solution effectively reduced bacterial load within minutes, outperforming competitor ophthalmic solutions in activity against <i>P. aeruginosa</i> and <i>E. coli</i>. Conjunctival swabs indicated a significant reduction in bacterial load post-treatment, confirming the solution's efficacy in reducing potential ocular pathogens. <b>Conclusions</b>: These findings highlight the potential of PHMB-based antiseptic solutions as a viable alternative to traditional disinfectants, particularly for preoperative prophylaxis and infection control. Further clinical trials are needed to confirm long-term safety and efficacy. The combination with cross-linked hyaluronic acid not only enhances tolerability but also extends antimicrobial action, making it a promising candidate for ophthalmic disinfection.