Comparative cytotoxicity potential of soft contact lens care products

Purpose. To determine the cytotoxicity potential of soft contact lens care products and benzalkonium chloride (BAK) by two colorimetric in vitro assays on an immortalized human corneal epithelial cell line (HCE-T). Methods. Four commercial soft contact lens care solutions were tested at 1: 3 dilution in growth medium. The positive controls for cytotoxicity were BAK in Dulbecco's phosphate buffered saline (DPBS) at 10, 5, 2.5, and 1.25 ppm and 1: 3 dilution of DPBS as negative control. Cell viability was assayed using a novel tetrazolium compound and an electron coupling reagent (MTS/PES), and by cell membrane integrity using neutral red dye uptake and release (NRUR). Mean spectrophotometric optical density of the test samples was compared to mean optical density of the controls at 24 and 48 hours of exposure to test product. Significance was measured by ANOVA/Tukey HSD test. Results. Cell viability and cell membrane integrity tests were not significantly different between lens care solutions and the negative controls for CIBA Vision SOLOcare (TM) PLUS, Advanced Medical Optics COMPLETE (R) Comfort PLUS (TM), or BAK at 1.25 ppm. Exposure to Bausch and Lomb ReNu MultiPlus((R)), Alcon OPTI- FREE (R) Express (R) with Aldox (TM), BAK 10, 5, and 2.5 ppm yielded significant reduction in cell viability and membrane integrity compared to negative controls. Discussion. Assays of HCE-T cell viability by MTS/PES, PES, and cell membrane integrity by NRUR cells yielded data that were similar to that previously reported with mouse L929 cells in tests based on the USP Elution Test. For the MTS/PES and NRUR assay methods, the solutions in order of increasing cytotoxicity potential were: SOLOCare = COMPLETE Comfort Plus < ReNu << OPTIFREE (R) Express((R)) with Aldox.