Cell viability of four corneoconjunctival cell lines exposed to five preservatives and a surfactant used for infection control in eyedrops.

The aim of this study was to evaluate the cytotoxicity of six ingredients used in eyedrops with regard to four corneoconjunctival cell lines. Cells were treated with the undiluted solution, and 2-fold, and 10-fold dilutions of each solution for 10, 30, and 60 min and cell viability was measured with the neutral red assay and the MTT assay. The degree of toxicity was based on the cell viability score (CVS). The CVS50 was determined by the number of measurements with a viability ≥ 50% of control. The CVS40/80 was calculated as follows: CVS40/80 = (number of measurements with a viability value >80%) - (number of measurements with a viability value <40%). Results were expressed as % of total measurements (%CVS). The results of each ingredient for %CVS50, and %CVS40/80 were 0.01% benzalkonium chloride (51, -13), 1% boric acid (100, 99), 0.4% methyl paraoxybenzoate (100, 100), 0.4% propyl paraoxybenzoate (100, 100), 1.0% polysorbate 80 (68, 18), and 0.5% chlorobutanol (100, 100). The use of benzalkonium chloride led to apparently low cell viability compared to the other five solutions.