Figure 5. HMGECs were differentiated for 48 h before exposure to latanoprost-BAK for 3 h. The bars in the graph are grouped into “triads” by latanoprost-BAK concentration levels (0.05–0.20, 0.5–2.0, 5.0–20, and 50–200 ug/ml). At low concentrations (0.05–0.20), neither latanoprost, BAK, nor their combination affected cell viability. At both mid-level concentrations (0.5–2.0 and 5.0–20 ug/ml), the toxicity of combined latanoprost-BAK was similar to that of BAK alone. At high concentrations (50–200 ug/ml), both latanoprost and BAK—individually and in combination—were lethal to the cells. In summary, within each triad, the effect of combined latanoprost-BAK was equivalent to that of its more toxic component, indicating that latanoprost and BAK exhibit no additive effect on toxicity. Significance markers are shown only within each triad of concentrations. There were nine replicates per condition. Latan: latanoprost; BAK: benzalkonium chloride; TX100: Triton-X 100 positive control; Dashed bar: p ≤ 0.001.