The pH of multi-purpose soft contact lens solutions

Contact lens patient discomfort has been linked to the pH of lens care solutions differing from that of tears. To determine if this is a potential problem with multi-purpose soft contact lens solutions, we used a Fisher Scientific Accumet 950 pH/ion meter (accuracy ±0.05 pH units) to measure the pH of 3 multi-purpose solutions-Alcon's Opti-One, Allergan's Complete, and Bausch & Lomb's ReNu. The resulting pH values were compared to the threshold for ocular awareness, which is outside the zone of 6.6 to 7.8, and the pH value of tears of 7.45. Each solution was dispensed and measured daily over a 23- to 36-day period using 15-ml increments to simulate the amount used on a daily basis. The average pH of solutions tested were 7.18 ± 0.02 for ReNu, 6.97 ± 0.02 for Opti-One, and 7.55 ± 0.02 for Complete. The highest and lowest pH values of all three multi-purpose solutions were found to be within the zone of ocular comfort and remained within a narrow value range throughout the testing period. Therefore, pH-induced discomfort is unlikely to occur when using these solutions on a daily basis. Nonetheless, practitioners should select lens care products carefully to ensure that the prescribed regimen meets the patient's needs.