Meibomian gland secretion plays a crucial role in the health of the ocular surface and function of the tear film. The lipid secreted by the meibomian glands has many crucial roles: 1) to retard evaporation from the preocular surface; 2) lower the surface tension of tears; 3) prevent spill-over of tears from the lid margin; 4) prevent the contamination of the tear film by sebaceous lipids; 5) prevent damage to the skin of the lid margin. In dry eye syndrome, blepharitis, meibomian gland dysfunction, and meibomitis the glands are the central pathophysiology of disease and thus a potential target for therapy.