PubMed · 11519338
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D Pop De Popa, M Alexescu, L Popescu. 2001. [Dry eye-blepharoconjunctivitis relationship].. https://pubmed.ncbi.nlm.nih.gov/11519338/
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PURPOSE: To determine the polar lipid composition of human meibomian gland secretions and their relationship to the preocular tear film. METHODS: Meibomian secretions were collected from normals and patients with chronic blepharitis. These lipids (meibum) were first separated by thin layer chromatography. Polar lipids were then separated utilizing high-pressure liquid chromatography with ultraviolet detection. Individual peaks were identified by comparison with standards. Collected sample peaks were subjected to differential transmethylation with sodium methoxide-methanol and the resulting fatty acid methyl esters were analyzed by gas chromatography-mass spectroscopy. RESULTS: Three phospholipids were identified as phosphatidylcholine, phosphatidylethanolamine and sphingomyelin; other unidentified phospholipids were also present. Also present in secretions were the sphingolipids ceramides and cerebrosides. Fatty acids present were 12-18 carbon chain length. All fatty acids were normal (not branched) saturated fatty acids except in sphingolipids, where hydroxy fatty acids were also present. Unsaturated normal fatty acids were present only in meibum from patients with meibomianitis. CONCLUSIONS: The composition of the polar lipids in meibomian gland secretions is more complex than previously thought. On the other hand, the type and carbon chain length of the polar lipid fatty acids appears strictly controlled. The relationship of these findings to the preocular tear film should be considered in terms of overall functionality. The polar lipid layer most likely is only one to three molecules thick and serves as a surfactant between aqueous tears and the thicker nonpolar lipid layer.
PURPOSE: To present our results to date on the evaluation of the pathophysiology of chronic blepharitis and its relationship to the tear lipid layer, and to propose a structure to that layer. METHODS: Compilation of work to date. RESULTS: A classification system of chronic blepharitis has been developed that has use in diagnosis, planning therapy, and assessment of mechanisms. Abnormalities in meibum have been identified that provide insight into disease mechanisms and have led to the development of a proposed structure to the tear lipid layer. A defect in polar lipids explaining the frequently associated evaporative dry eye has been identified. Mechanisms accounting for the therapeutic benefit of minocycline have been elucidated. CONCLUSION: Chronic blepharitis has associated meibum abnormalities that explain defects in the tear lipid layer that may result in a frankly unstable tear film and that explain the frequently associated evaporative dry eye.
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