Meibomian gland dysfunction

Meibomian gland dysfunction (MGD, also meibomitis or meibomianitis) is a chronic disease of the meibomian glands, which is commonly characterized by obstruction of the end of the duct that delivers the secretion produced by the glands (called meibum) to the eye surface, which prevents the glandular secretion from reaching the ocular surface. The dysfunction could be that the amount of secretion produced may be abnormal (either too little or too much meibum produced).

Source: Wikipedia — Meibomian gland dysfunction (CC BY-SA 4.0)