Practical considerations in the use of hydrogen peroxide disinfection systems

Three studies were conducted to evaluate the effectiveness of hydrogen peroxide (H2O2) neutralization in returning the pH of the soft contact lens soaking solution to that of tears (pH 7.4). In the initial study, we evaluated seven different brands of H2O2 disinfection systems. The final pH of the seven systems ranged from 6.15 to 7.74, with two systems having values outside the threshold for ocular discomfort. The final residual H2O2 concentrations ranged from 0 to 70 ppm (parts per million), five of the seven having residual concentrations of 0 to 3 ppm. In the second part of the study, we evaluated the pH of four H2O2 systems over 4 weeks of daily use. The end-point pH of the H2O2 systems did not change significantly over the 4-week period, although two of the systems were consistently closer to the physiologic pH of tears than were the other two. In the third part of the study, four brands of over-the-counter (OTC) 3% H2O2 were substituted into six different H2O2 disinfection systems. The manufacturer's recommended H2O2 was used as a control. There were wide variations in initial pH and significantly lower end-point pH levels with the OTC preparations.