Impact of short-term exposure of commercial eyedrops preserved with benzalkonium chloride on precorneal mucin

Purpose: The aim of this study is to investigate the short-term effects of benzalkonium chloride (BAC), a preservative used in many ophthalmic topical solutions, on precorneal mucin in humans. Methods: Immortalized human corneal-limbal epithelial (HCLE) cells were exposed to eyedrops containing BAC solutions at 0.0025% and 0.01% concentrations for a period of 15 min. Human corneal epithelium was acquired with consent, as a by product of elective excimer photorefractive keratectomy procedures after application of Ocuflox® eyedrops (0.3% ofloxacin with 0.0025% BAC) for 1 week before surgery. The relative expression of the MUC1 and MUC16 mucin gene was determined by conventional and real-time reverse transcription-polymerase chain reaction (RT-PCR). Monoclonal antibodies for MUC1 (HMFG-1) and MUC16 (OC125) were used in western blot analysis to detect MUC1 and MUC16. Human corneas exposed to 0.01% BAC solutions were examined by transmission electron microscopy. Results: The expression of MUC1 and MUC16 gene transcripts was not changed after exposure to BAC in HCLE cells and human corneal epithelium. However, MUC1 and MUC16 were reduced after exposure to BAC in HCLE cells and human corneal epithelium. Transmission electron microscopy of the anterior corneal surface revealed fixation of the mucous layer after exposure to 0.01% BAC for 5 or 15 min; prolonged exposure (60 min) to 0.01% BAC destroys the mucous layer. Conclusions: This study demonstrates that short-term exposure to BAC can alter the precorneal mucin.