Lipidlagen

Lipidlagen is a term used to describe a thin layer of lipids that forms a hydrophobic barrier at biological interfaces. The most well-known example is the outer lipid layer of the tear film covering the eye’s surface, where it is produced primarily by the Meibomian glands. This lipid layer sits on top of an aqueous and mucin-containing layer and helps reduce evaporation, stabilize the tear film, and improve optical quality.

In the tear film, the lipidlagen consists mainly of nonpolar lipids such as wax esters and cholesterol esters, with smaller amounts of cholesterol and other lipids that help organize the layer and interface with the underlying aqueous layer. The precise composition and structure can influence tear film stability and susceptibility to evaporative dry eye.

Lipidlagen is not limited to the eye. The term is sometimes used more generally to describe lipid barriers that protect surfaces in other tissues, most notably the skin. In the skin, a lipid matrix composed of ceramides, cholesterol, and free fatty acids forms a barrier that helps prevent excessive water loss and provides protection against environmental insults. In cell biology, a related concept is the lipid bilayer that forms the core structure of cellular membranes, creating compartments and regulating substance exchange.

Clinical relevance includes disorders of lipidlagen such as evaporative dry eye and impaired skin barrier function. Assessment methods for tear film lipid layer include interferometry and tear breakup time testing.

See also: lipid bilayer, tear film, Meibomian glands, dry eye, skin barrier.