Clinical aspects of topical application of dilute hydrogen peroxide solutions

Because hydrogen peroxide (H2O2) is a widely used microbicidal agent for contact lens disinfection, it is important to assess its effect on ocular tissues at the levels that can be associated with the use of these systems. Three recently reported clinical studies provide new information on this subject: In the first study, the discomfort threshold for a range of H2O2 concentrations administered to the eye was explored. The mean thresholds for 10 subjects were 267 ppm H2O2 for 55% water content contact lenses soaked in the solution and 282 ppm for 38% water content contact lenses. Hydrogen peroxide disinfection systems are designed to have residual H2O2 concentrations in the eye of no more than 50-60 ppm, allowing for an adequate safety margin. The stinging occasionally reported after lens disinfection may be due to factors other than residual H2O2. In the second study, the rate of in vivo neutralization of H2O2 administered to the eye was studied. Removal of 50 ppm H2O2 from a hydrogel lens was completed within the first 30 seconds of human wear when the eyelids were held closed, and within 60 seconds during wideopen gaze, with blinking every 5 seconds. In the third study, the corneal permeability to fluorescein was determined in 10 subjects after dosing with 50 ppm H2O2, 500 ppm H2O2, as well as negative and positive controls. There was no significant difference between the negative control and the two H2O2 concentrations, whereas the positive control was different from all other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)