Meibomian glands (often written with a small "m" and also called tarsal glands) are holocrine type exocrine glands, along the rims of the eyelid inside the tarsal plate. They produce meibum, an oily substance that prevents evaporation of the eye's tear film. Meibum prevents tears spilling onto the cheek, trapping the tears between the oiled edge and the eyeball, and making the closed lids airtight. There are about 50 glands on the upper eyelid and 25 glands on the lower eyelid.
Front of left eye with eyelids separated to show medial canthus and openings of tarsal (meibomian) glands
The glands are named after Heinrich Meibom (1638–1700), a German physician.
The biochemical composition of meibum is extremely complex and very different from that of sebum. Lipids are universally recognized as major components of human and animal meibum. Recently, an update on the composition of human meibum and on the structures of various positively identified meibomian lipids was published.
In humans, more than 90 different proteins have been identified in meibomian gland secretions.
Dysfunctional meibomian glands often cause dry eyes, one of the more common eye conditions. They may also contribute to blepharitis. Inflammation of the meibomian glands (also known as meibomitis, meibomian gland dysfunction, or posterior blepharitis) causes the glands to be obstructed by thick waxy secretions. Besides leading to dry eyes, the obstructions can be degraded by bacterial lipases, resulting in the formation of free fatty acids, which irritate the eyes and sometimes cause punctate keratopathy.
Meibomian gland dysfunction is more often seen in women and is regarded as the main cause of dry eye disease. Factors that contribute to meibomian gland dysfunction can include things such as a person's age and/or hormones or severe infestation of Demodex brevis mite. Treatment can include warm compresses or expression of the gland by a professional. Lifitegrast and Restasis are topical medication commonly used to control the inflammation and improve the oil quality. In some cases topical steroids and topical/oral antibiotics are also prescribed reduce inflammation. Intense pulsed light (IPL) treatments have also been shown to reduce inflammation and improve the gland function in patients. Meibomian gland probing is also used on patients which experience deep clogging of the glands.
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