Comparison of Osmolality Values of Selected Ocular Lubricants

Abstract

Abstract: : Purpose: Osmolality is a physical property of artificial tear preparations that may be associated with ocular irritation upon instillation. Previous studies have shown that when the tear film of a dry eye patient is hyperosmolar, a hypo–osmolar artificial tear preparation provides greater symptomatic relief than iso–osmolar preparations. The osmolality of common ocular lubricants has not been widely reported; thus, the purpose of this investigation is to not only report the osmolality values of several marketed ocular lubricants, but to determine if there is a statistically significant difference between agents. Methods: Twenty–one different lubricating agents were examined in this study; approximately one–third being preservative free and the remaining containing either a standard preservative or a transient preservative. All products were unopened and unexpired prior to testing. Osmolality was measured using the Wescor VAPRO Vapor Pressure Osmometer. Results: Twenty of the twenty–one products tested had mean osmolality values within the range of 235.33 to 354.83 mmol/kg. However, data analysis using ANOVA multiple variables and applying Tukey’s multiple mean comparisons showed that one product fell outside this range and varied significantly from others in the group. Thera Tears with a mean value of 181.13 mmol/kg was significantly lower than the means of other products and statistically significant at the 95% confidence level. Conclusions: Previous studies have shown conflicting evidence concerning the significance of artificial tear osmolality in the management of dry eyes. Some suggest that patients report no difference in symptomatic relief from either iso– or hypo–osmolar tear preparations, while other studies show that there is a clear preference for hypo–osmolar agents. The current study reports values measured for 21 common ocular lubricants and shows that Thera Tears has an osmolality value statistically significantly lower than all other products tested.

Keywords: cornea: tears/tear film/dry eye