Morphology and function of the inner lid margin – History and recent findings

Purpose The eyelid margin is a region that often receives little interest but, in contrast, is of utmost importance for ocular surface health and disease. The posterior lid border is a pre‐requisite for perfect distribution of a thin pre‐ocular tear film that is reformed with every blink. Methods Own findings on the zonal differentiation of the normal lid margin and observations in pathology are presented in the context of the literature on this region. Results The lid margin is not a homogenous entity but composed of different sub‐zones which comprise at least the anterior and posterior lid borders as opposed to the free lid margin. The posterior lid border is again subdivided into three zones that are all characterized by a specific epithelial structure. The termination of the cornified epidermis posterior to the orifices of the Meibomian glands (MG) explains hyperkeratinization as the main pathology of the MG. The mucocutaneous junction (MCJ) has a parakeratinized surface that represents the natural stainable line of Marx. The inner aspect of the posterior lid border is covered by the epithelial lip of the lid wiper with conjunctival structure and goblet cells. The line of Marx, proposed as the bottom of the tear meniscus, has occasionally been suggested as the area wiping over the globe but several lines of evidence point to the lid wiper as the contact interface between lid and globe. Conclusion Better knowledge of the structure and function of the eyelid margin will provide better tools for the understanding of its function, clinical diagnosis and therapy of frequent diseases at the ocular surface, namely dry eye disease. Support DFG KN 317‐11