[Meibomian glands : part III. Dysfunction - argument for a discrete disease entity and as an important cause of dry eye].

Meibomian gland dysfunction (MGD), mainly synonymous with posterior blepharitis but typically without prominent inflammatory alterations of the lid margin, is a discrete disease entity and a frequent cause of wetting deficiencies of the ocular surface leading to dry eye disease that deserves increased recognition by clinicians. The history, classification, pathology, influencing factors, diagnostics and therapy are explained and discussed. MGD is mainly based on an obstructive mechanism caused by hyperkeratinization of the excretory duct and/or increased viscosity of the secretion (meibum) with subsequent deficiency of the tear film lipid layer. MGD is influenced by the hormonal status and by chemical and mechanical noxes as well as genetic defects and it occurs more frequently in women and generally increases with age. It results in stasis of meibum inside the glands, dilatation of the ductal system and eventually in atrophy and loss of glandular tissue (gland dropout). Careful investigation of the eyelids and lid margins with eversion, if necessary, should therefore be performed in every case of a wetting defect, notably before fitting contact lenses. Particularly important is the inspection of the meibomian orifices and diagnostic expression by mild mechanical compression of the lid.