Abstract
Purpose :
Meibomian gland dysfunction (MGD) contributes to dry eye which affects 16 million people in the U.S. Meibum lipids are important for the stability of the tear film. The cholesteryl ester/wax ester (CE/WE) ratio decreases with MGD but it is unclear if or how CE affects meibum structure or tear film stability. The aim of this study was to bridge this gap in knowledge.
Methods :
Meibum was collected from a 66-year-old Caucasian and a 29-year-old black donor and CE and WE were separated by MgO column chromatography. The esters were characterized using 1H-NMR and the structure, conformation and phase transitional parameters of mixtures with a range of CE/WE ratios was determined using Fourier transform infrared spectroscopy.
Results :
: CE and WE were completely separated. WE from the older donor A (Awe) was composed of 16 % less straight-chains and 50 % more iso-chains compared with CE from the same donor (Ace). The phase transition temperature and order (stiffness) for WE and CE from the younger donor B, Bwe and Bce, respectively, were higher, P > 0.0001, compared to Awe and Ace. Bwe added to Bce, decreased the hydrocarbon chain order, and phase transition temperature of Bce, P < 0.05. Increasing amounts of Bce added to Bwe caused the hydrocarbon chain order and phase transition temperature to increase linearly above 20 % Bce. The opposite trends were apparent for the donor A samples. The reason for the opposite trends is that Ace was more fluid, P = 0.02, compared to Awe, while Bce was less fluid, P > 0.0001, compared with Bwe.
Conclusions :
Meibum CE and WE can be completely separated. CE changes the phase characteristics of meibum depending on whether it is more or less ordered, than WE. Changes in the meibum content of CE could explain changes in meibum order with age and MGD which may influence tear film stability. Studies to separate CE and WE from meibum are warranted to determine if/how meibum CE and WE conformation and composition change with age, gender, race and MGD and if the changes are related to tear film stability.
This is a 2021 ARVO Annual Meeting abstract.