Purpose: Tear film lipid layer (TFLL) is a very structured layer with essential functions. Its structure is highly dependent on chemical and physical characteristics of lipids composing the TFLL We previously published alterations in the composition of TFLL in patients suffering from meibomian gland dysfunction (MGD). Branched chain fatty acids (BCFA) were significantly increased, suggesting that BCFA may be associated with the disease. The aim of this study was to evaluate the effect of a treatment by oral minocycline associated to lid hygiene versus lid hygiene only on changes in ocular surface abnormalities and in meibomian fatty acid composition in patients suffering from MGD. Methods: Twenty individuals suffering from MGD were followed before and after 8 weeks of minocycline treatment associated to lid hygiene (n=10) or lid hygiene only (n=10). Break-up time (BUT), corneal staining, and the quality of meibomian excreta were evaluated before and after treatment. Meibomian secretions were collected at the end of the study using a sterile Schirmer paper strip, and submitted to derivatization with a transmethylating agent. Methyl esters were subsequently analyzed by gas chromatography (GC) and GC mass spectrometry. Results: Minocycline significantly improved BUT in MGD patients (p=0.03) The proportion of one branched-chain fatty acid (isoC20) was significantly decreased in meibomian secretions from MGD patients treated with minocycline (-65%) or lid hygiene only (-25%). No significant effect was observed for the other fatty acids. Conclusions: This study reported that a treatment with minocycline, or even lid hygiene only, significantly improved tear film stability in patients suffering from blepharitis that may be associated with changes in the fatty acid profile of meibomian secretions. Minocycline was more powerful than lid hygiene alone to reverse the increase in branched chain fatty acids in MGD patients. IsoC20 may be a valuable marker of MGD and treatment efficiency in MGD patients, and might be associated with the improvement of the symptoms in the patients.