Meibomian refers to a particular type of gland in the eyelids. There are about 25 to 40 meibomian glands in the upper eyelid and 20 to 30 in the lower eyelid. The function of these glands is to secrete oils, which help keep the tears from evaporating too quickly.
Meibomian gland dysfunction is blockage or some other abnormality of the meibomian glands so they don’t secrete enough oil into the tears. Because the tears then evaporate too quickly, MGD is a leading cause of dry eye syndrome. It also is associated with an eyelid problem called blepharitis.