Healthy Meibomian glands that line your upper and lower eyelids secrete oil with every blink. This oil, or lipid, serves as a critical component of a healthy tear film in that it helps prevent tear film evaporation. When the glands are not functioning correctly, it is called Meibomian Gland Dysfunction, or MGD. MGD is a leading cause of Dry Eye Disease and can be the source of dry eye symptoms, such as burning, stinging, and itching. However, even patients without symptoms (asymptomatic) could have MGD.