Historical overview on the distribution of major lipid classes in human meibum.

SE, sterol ester; WE, wax ester; TAG, triacylglycerides; DE, diesters; FFA, free fatty acid; PL, phospholipid; SL, sphingolipid; OAHFA, (O-acyl)-ω-hydroxy-fatty acid.
‡PL refers to sum total of PC, phophatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PG, phosphatidylglycerol.
†SL refers to sum total of SM, sphingomyelin; CER, ceramides; GluCer, glucosylceramide; DihexCer, dihexosylceramide. Values presented for the current study represent percentages of individual lipid classes in the meibum from normal volunteers.
*The quantity of WE is subjected to the use of palmityl palmitate as an internal standard.
aAnalyses were conducted on pooled samples.
bEstimate was given for total polar lipids excluding free fatty acids.
cEstimate referred specifically to cerebroside content.