Meibomian glands are holocrine type exocrine glands, along the rims of the eyelid inside the tarsal plate. They producemeibum, an oily substance that prevents evaporation of the eye'stear 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. Dysfunctional meibomian glands often cause dry eyes, one of the more common eye conditions. They may also contribute to blepharitis. The glands are named after Heinrich Meibom, a German physician, who first described them.
Function
Meibum
Lipids
s are the major components of meibum. The term "meibum" was originally introduced by Nicolaides et al. in 1981. 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. Currently, the most sensitive and informative approach to lipidomic analysis of meibum is mass spectrometry either with direct infusion or in combination with liquid chromatography.
Proteins
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 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 brevismite. 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 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. Meibomian gland dysfunction may be caused by some prescription medications, notably isotretinoin.
