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We evaluated the pH of four hydrogen peroxide systems over a 28-day period of normal daily use to determine if pH changes occurred which could cause ocular discomfort. Using a Corning Model 10 pH meter, we measured the initial pH of the disinfection and neutralization solutions and the final pH of the neutralization solutions over each system's disinfection and neutralization cycle. The final pH of the four systems did not change significantly over the 28-day period; however, the final pH of two of the hydrogen peroxide systems were consistently closer to the physiological pH of tears than the other two systems evaluated. These findings suggest that initial discomfort experienced over a 28-day period of normal daily use of any of the hydrogen peroxide disinfection systems studied may be due to the individual system used, but not due to pH changes within a system. However, individual sensitivities to pH should be considered.