Human Meibum Cholesteryl and Wax Ester Variability With Age, Sex, and Meibomian Gland Dysfunction

PURPOSE: Relationships between tear film lipid (TFL) layer composition, structure, and function could provide insight into the etiology of dry eye. The molar ratio of cholesteryl ester (CE)/wax ester (WE) was measured in meibum from normal donors (M(n)) and compared with meibum from donors with meibomian gland dysfunction (M(MGD)). METHODS: CE/WE was measured using nuclear magnetic resonance spectroscopy. RESULTS: CE/WE was distributed into two populations with 81% distributed near 0.55 and 19% near 0.3. CE/WE were higher in donors 13 to 19 years old compared with donors 1 to 12 years old and 20 to 88 years old. CE/WE for M(MGD) was 30% lower, 0.34 ± 0.04, compared with M(n), 0.49 ± 0.04. There were no sex differences in CE/WE. There were no significant racial differences between the CE/WE ratios for Asians and Caucasians. The CE/WE ratio was higher for blacks and lower for Hispanics compared to Caucasians. Due to the small number sampled, confirmation of the later racial results is needed. The packing of CE and WE in the TFL layer was proposed. CONCLUSIONS: Although M(MGD) contains much less CE than M(n), factors other than the CE content, such as the levels of saturation and/or proteins, may be responsible for the higher order of M(MGD). In addition to saturation, CE could contribute to the increase in order of M(n) between 0 and 20 years of age. Observed changes in the meibum content of CE alone is not likely to influence tear film stability.