Abstract
Abstract: :
Purpose:To determine if amount of specific non-polar lipids in meibum is associated with patient dry eye signs. Enhanced separation and detection methods would be expected to result in sensitivities greater than was achieved with previous methods. Methods: In order to enhance lipid separations, patient meibomian gland lipid (meibum) samples were first separated into lipid classes by aminopropyl silica solid phase extraction (SPE). Each of the resulting lipid fractions was further separated by HPLC with detection by evaporative light scattering detection (ELSD). Lipids were identified by elution pattern and comparison with standards. Detection and quantitation of these lipids by ELSD rather than UV spectroscopy increased sensitivity for lipids with low UV absorbance. Results: The amount of meibum monoglycerides was associated with blepharitis patient meibomian gland dysfunction (including lower volume and higher viscosity) and dry eye signs (as confirmed by evaporometer values). Dry eye patient monoglyceride level was more than twice that of normal individuals. Conclusion: It is known that monoglycerides form gels of variable and sometimes high viscosity depending on monoglyceride type, water content and temperature. However in the presence of triglycerides (diglycerides are less effective than triglycerides) these viscous gels are not formed. Alternately, with hydrophilic co-emulsifiers such as the fatty acid salts (e.g. sodium oleate), or other surface-active compounds, a thixotropic emulsion results. Our findings not only suggest that some types of dry eye are the result of excessively high monoglyceride levels in meibum but published research also suggests likely mechanisms. Thus, lipase action with triglyceride (or diglyceride) substrates is one source of monoglycerides. Therefore it is suggested that some types of dry eye may be effectively treated with triglycerides, lipase inhibitors, or specific co-emulsifiers.
Keywords: 376 cornea: tears/tear film/dry eye • 458 lipids • 437 inflammation