Anatomy of the Meibomian gland

Purpose The Meibomian gland (MG) is a large sebaceous gland in the eye lid that produces the lipids for the superficial tear film layer. Although it is an indispensable component of the functional anatomy of the ocular surface, its importance is still underestimated. Increasing evidence points to a high impact of MG dysfunction (MGD) as a major cause of a dysfunctional tear film and evaporative dry eye disease. Increasing new information has occurred in recent years an will be explained. Methods Results of a Pubmed based literature review on the anatomy, cell biology and physiology are explained together with own results. Results The Meibomian gland shares distinct similarities in embryology with the pilo‐sebaceous unit of the cilia. The keratinised skin epithelium extends into the terminal part of the central duct. Signs of incipient keratinisation continue downstream in the central duct and ductules. The innervation of the MG is characterized by the structure of a dense network of nerve fibres and terminals around the basement membrane of the secretory acini and ducts. The MG is, similar to the lacrimal gland, mainly under parasympathetic control. The orifice of the central duct opens onto the free lid margin close to the posterior lid border and directly anterior to the line of Marx, that represents the surface of the muco‐cutaneous junction which is followed proximally by the epithelial lip of the lid wiper Conclusion The MG is the provider of the superficial lipid layer of the tear film and is regulated similar to the lacrimal gland which may allow coordinated secretion. It preserves a commitment to keratinisation which explains why hyper‐keratinisation of the MG is an important cause for obstructive MGD. Deeper knowledge of the MG will allow better understanding of MGD and its therapy.