Anatomy, physiology and pathophysiology of the meibomian gland

Abstract Purpose The sebaceous meibomian glands (MG) in the eyelids, that secrete lipids for the superficial tear film layer, are of increased scientific and clinical interest. The recent MGD report of the non‐profit organization Tear Film and Ocular Surface Society (TFOS, www.tearfilm.org) revealed that MG Dysfunction (MGD) with lack of tear film lipids and the resultant evaporative type of dry eye is the main underlying reason for the wide‐spread dry eye disease that affects millions of patients world wide Methods A literature review based on the TFOS MGD Report together with own findings is discussed in order to explain the anatomy, physiology, pathophysiology and clinics of MGD. Results MGD is a multifactorial disease based on endogeneous and exogeneous factors that interact in self propagating vicious circles. Advancing age, female sex, environmental factors such as topical medication, bacterial influences and probably subclinical inflammatory pathways as well as contact lens wear are some main factors lead to the onset and propagation of MGD. These result in hyperkeratinization of the gland epithelium as well as increased viscosity of the secretum. Together this results in the obstructive type of MGD. Two effector arms of obstruction lead to a primary lack of oil on the tear film with downstream evaporative dry eye but also to a secondary hidden degeneration of the glandular tissue inside the lids that results in gland atrophy. Conclusion Obstructive MGD with downstream lipid deficiency is now recognized as the main cause for dry eye disease and this achievement of the TFOS MGD Workshop has already changed/revolutionized our view on dry eye disease as well as lead to several new developments for diagnosis and treatment that specifically address MGD. Support DFG KN 317‐11