Meibomian gland Meibomian gland The Meibomian glands (often written with a small "m" and also called tarsal glands) are a holocrine type of exocrine glands, at the rim of the eyelids inside the tarsal plate, responsible for the supply of meibum, an oily substance that prevents evaporation of the eye's tear film. Meibum prevents tear spillage onto the cheek, trapping tears between the oiled edge and the eyeball, and makes the closed lids airtight. There are approximately 50 glands on the upper eyelids and 25 glands on the lower eyelids. Dysfunctional meibomian glands often cause dry eyes, one of the more common
Sealant performing these functions. A sealant may be viscous material that has little or no flow characteristics and which stay where they are applied; or they can be thin and runny so as to allow it to penetrate the substrate by means of capillary action. Anaerobic acrylic sealants (generally referred to as impregnants) are the most desirable, as they are required to cure in the absence of air, unlike surface sealants that require air as part of the cure mechanism that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire,