Dry eyes may be due to a lack of tear production. This form is particularly common in post-menopausal women. But most of the time, it’s the result of a qualitative deficit in the tear film: the lipid layer, essential for maintaining the aqueous layer, is of insufficient quality or quantity, and tears evaporate too quickly. In over 80% of cases, the cause is a dysfunction of the Meibomian glands (DGM).
There are 30 to 40 Meibomian glands per eyelid. Located on the posterior surface of the eyelids, they emerge behind the eyelashes, on the free edge. They secrete meibum, a fatty substance composed mainly of triglycerides, which forms the lipid layer. By preventing evaporation of the aqueous layer, it keeps the eye hydrated and lubricated. When the meibomian glands malfunction, their secretions thicken, leading to occlusion of their orifices, a decline in the quality of the lipid layer and, ultimately, permanent atrophy of the meibomian glands.