Cytotoxicity of hydrogen peroxide to human corneal epithelium in vitro and its clinical implications

We investigated the cytotoxicity of hydrogen peroxide by exposing primary confluent cultures of human corneal epithelium to a single dose of this agent at concentrations ranging from 30 ppm to 100 ppm in the tissue culture medium. Our criteria for cytotoxicity included alterations in cytokinesis and movement of the cells, changes in cell morphology, and mitotic index, and cell degeneration and death. At a concentration as low as 30 ppm, hydrogen peroxide caused rapid cell retraction as well as cessation of cytokinesis and mitotic activity; formation of membranous vesicles preceded cell death, which occurred by seven to eight hours after exposure. At a concentration of 50 ppm, normal cell activity ceased almost instantaneously; numerous surface vesicles formed by 1.5 hours of exposure, and the cells died within four to five hours. Higher concentrations (70 to 100 ppm) of hydrogen peroxide caused cell death within a few minutes. Because neutralization of hydrogen peroxide and patient compliance with the manufacturer's instructions are critical in the proper use of peroxide-based disinfection systems, users should be aware of possible short- and long-term iatrogenic toxicity of residual peroxide on the cornea.