The role of wax and sterol esters of meibomian secretions in chronic blepharitis

We analyzed the fatty wax esters and sterol esters found in the expressed lipid secretions of six patients from each of six clinical groups of chronic blepharitis, plus eight normal controls. Using gas liquid chromatography (GLC), 12 peaks corresponding to equivalent chain lengths (ECL) of 33.6, 35.4, 36.1, 37.3, 38.2, 39.2, 40.1, 41.2, 42.1, 43.2, 44.9 and 45.7 were found in the fatty wax esters and five peaks corresponding to ECL 19.1, 20.2, 21.1, 22.0 and 23.2 were found in the sterol esters. The clinical groups showed significant differences in several of these components. Sterol and wax esters represent the largest fraction of the total meibomian lipid secretion. The finding that the blepharitic groups exhibit biochemical differences in the distribution of these esters indicates that the esters may play a role in the disease process, perhaps by providing a preferential substrate for normal flora which we have shown to have lipolytic capabilities. The resultant de-esterification could alter the tear film and contribute to ocular irritation. In addition, the differences seen in the composition of the ester fraction of the meibomian secretion could lead to differences in melting point, which, in turn, could affect viscosity and surface tension of the tear film, leading to changes in breakup time and to secretion stagnation within glands.