Comparison of pH Values of Selected Ocular Lubricants

Abstract

Abstract: : Purpose: The physiologic pH of blood and tears is approximately 7.4. This value is often viewed as the optimal target pH for comfort and safety of ocular solutions. Additional considerations such as product stability and efficacy may, however, be of greater importance than comfort in determination of the product’s final pH. Although artificial tears have long been the typical treatment for dry eyes; very little information has been reported regarding pH of these products. It is the purpose of this investigation to report these values and to determine if there is a significant difference between the marketed agents studied. Methods: Twenty–six commercially available lubricating agents of varying viscosity were examined. All products were unopened and unexpired prior to testing. pH was measured using the Cardy Twin pH Meter Kit by Horiba Instruments, Inc. Results:Most products tested had a mean pH within the range of 6.91 to 7.38. Data analysis using ANOVA multiple variables and applying Tukey’s multiple mean comparisons showed that six products fell outside this range and varied significantly from others in the group. Optics Laboratory Mini–Drops with a pH of 4.78 and Optics Laboratory OcuFresh Eye Shower with a pH of 5.44 had the lowest values measured. Values for four other products ranged from 6.16 to 6.63. Results were statistically significant at the 95% confidence level. Conclusions: While most researchers agree that an artificial tear preparation with a pH near 7.0 is well tolerated by dry eye patients, it has also been reported that a near iso–tonic alkaline preparation may be preferred by patients with moderate to severe dry eyes. The current study reports pH values for 26 contemporary products. It demonstrates that most artificial tear samples have a pH ranging from neutral to acidic with Optics Laboratory Mini–Drops and OcuFresh Eye Shower having the lowest pH of the agents studied. Future studies should determine whether an acidic or an alkaline pH formulation offers a greater comfort and/or therapeutic benefit.

Keywords: cornea: tears/tear film/dry eye