Evaluation of corneal damage caused by iodine preparations using human corneal epithelial cells

Purpose To compare the cytotoxicity of povidone–iodine solution (PVP-I) with that of polyvinyl alcohol–iodine solution (PAI) for ophthalmic use. Methods Cells of the human corneal epithelial cell line HCE-T were exposed to various dilutions of PVP-I or PAI, and the cytotoxicity of these two antiseptics was evaluated. The relative toxicities of PVP-I and PAI were also investigated following the inactivation of iodine by achromatization with sodium thiosulfate. Results PVP-I and PAI had equivalent antiseptic effects, but the cytotoxicity of PVP-I diluted 16-fold was higher than that of PAI diluted 6-fold. Following inactivation of iodine with sodium thiosulfate, the cytotoxicity of PVP-I remained concentration dependent, whereas PAI exhibited a low toxicity that was similar to the effect of saline on cell viability. Exposure to lauromacrogol, a surfactant used in PVP-I, in solution at concentrations of 1–1000 mg/mL clearly resulted in corneal cytotoxicity. The PVP-I and PAI solutions had a pH value of 4.0 and 5.2, respectively. HCE-T cells were significantly more viable at pH 7 than at pH 1–6. Conclusion To avoid corneal damage, preoperative antisepsis of the surgical field should be accomplished with PAI diluted 6-fold, rather than with PVP-I diluted 16-fold. The toxicity of the iodine compound stems primarily from the available iodine concentration and partly from its pH, surfactant and osmolality. Further clinical investigations are required in order to determine the optimal concentrations for use.