Fig. 1. In vitro eye irritatioin test - Neutral Red Uptake assay. In vitro eye irritation test was performed using Balb/c 3T3 cell line. The cells were treated with increasing concentrations of lomefloxacin ranged from 1 to 20mg/ml and then incubated in 96 well plates for 24 h before Neutral Red. A positive control group was set up with sodium dodecyl sulphate (SDS) ranged from 0.0125 to 0.1%. After an additional 3 h incubation periods the optical density of the NR extract was measured at 540 nm using a microtiter plate reader. The concentration producing 50% inhibition for neutral red uptake was calculated. Values represent the mean ± SD of duplicate determinants from one of three representative experiments. ** P < 0.01 as determined by Dunnett Multiple Comparisons test as compared to vehicle control group. Inset, A plot of the log of the % viability versus concentration of lomefloxacin in order to the IC₅₀ value.