The antibacterial effect of topical anesthetic proparacaine on conjunctival flora

Purpose: To investigate the antibacterial effect of topical anesthetic proparacaine on conjunctival flora. Methods: One hundred and forty-four eyes of 72 patients awaiting cataract surgery were included in the study. A commercially available solution of proparacaine, preserved with benzalkonium chloride 0.01%, was instilled in one eye of all subjects while the vehicle solution, including the same concentration of preservative in aqueous solution, was administered to the other eye. Conjunctival cultures were taken from all eyes before and 15 minutes after the instillation of proparacaine and the vehicle. Results: Of the 144 eyes, 76 (52.8%) had positive-conjunctival cultures with the most commonly isolated organisms being coagulase-negative staphylococci in each group. Of the 76 culture-positive eyes, 40 (52.6%) received proparacaine and 36 (47.4%) the vehicle preparation. Fifteen minutes after the instillation of proparacaine and the vehicle eyedrops, four eyes (10%) and 12 eyes (33.3%) had culture-positive conjunctival smears, respectively. Proparacaine significantly reduced the number of culture-positive eyes (p = 0.0003), in contrast to the vehicle (p = 0.21). Conclusion: A topical anesthetic, proparacaine, demonstrates antibacterial effects on the conjunctival flora.