Abstract: Both aqueous tear deficiency and increasing evaporation lead to dry eye. The outmost part of the tear film is the lipid layer secreted from the meibomian glands. The meibomian lipids maintain the stability and prevent evaporation of the tear film. The composition and construction of lipid layer influence the stability of itself. In the patients with meibomian gland dysfunction (MGD), the dysfunction of lipid layer leads to the reducing stability of tear film and destruction of ocular surface, and finally cause the overevaporation dry eye.   (Int Rev Ophthalmol, 2014, 38:    316-319)