Study: What's different about MGD

This study is no less welcome for having results that are kind of self-evident, i.e. if you've got MGD, your oil composition will be different. If it helps lead to a better diagnostic methodology that picks up on MGD, so much the better, though I still say, docs really oughtta get more hands-on teaching about the physical signs of lid margin disease in school.

Differences in meibomian fatty acid composition in patients with meibomian gland dysfunction and aqueous-deficient dry eye.
Joffre C, Souchier M, Grégoire S, Viau S, Bretillon L, Acar N, Bron AM, Creuzot-Garcher C.
Br J Ophthalmol. 2008 Jan;92(1):116-9

AIMS: To evaluate the differences in meibomian fatty acid composition in healthy subjects and in patients suffering from meibomian gland dysfunction or aqueous-deficient dry eye.
METHODS: We collected meibomian oil using a sterile Schirmer paper in healthy individuals (n = 20), dry eye patients (aqueous-deficient) (n = 32) and meibomian gland dysfunction (MGD) patients (n = 25) after gentle massage of the lid margin. Meibomian fatty acids were directly transmethylated and analysed using gas chromatography (GC) and GC mass spectrometry.
RESULTS: Meibomian fatty acids were similar in healthy individuals and in dry eye patients but were different in MGD patients, who showed significantly higher levels of branched-chain fatty acids (29.8% vs 20.2%) (p<0.0001) and lower levels of saturated fatty acids (9.3 vs 24.6%) (p<0.0001), in particular lower levels of palmitic (C16) and stearic (C18) acids.
CONCLUSION: The increase in branched-chain fatty acids may reflect greater quantities of wax and cholesterol esters and triglycerides in meibomian gland excreta. Since wax and cholesterol esters are the main lipids of meibum, these differences may have physical consequences for tear-film lipid-layer fluidity and stability. Meibomian fatty acid composition and particularly the increase in branched chains could be a marker for meibomian gland dysfunction.