Permeability of rabbit corneal epithelium to horseradish peroxidase after the influence of benzalkonium chloride.

A tight barrier against permeation of horseradish peroxidase into the corneal epithelium exists at the corneal surface adjacent to the tear film. The present light and transmission electron microscopic study reveals that the cationic surfactant, benzalkonium chloride, which is commonly added to eye drops as a preservative, breaks down this barrier. Lysis of the cell membranes was demonstrated, resulting in a leakage of the tracer into and underneath the superficial cells. The grade of cellular destruction caused by benzalkonium chloride was dependent upon the concentration and exposure time of the drug.