Meibomian gland

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Meibomian gland
Gray1205.png
Front of left eye with eyelids separated to show medial canthus and openings of tarsal (meibomian) glands.
Latin glandulae tarsales
Gray's p.1026
MeSH Meibomian+glands
Anatomical terminology

The meibomian glands (or tarsal glands) are a special kind of sebaceous gland 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.[1] 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 eye conditions. They may also contribute to blepharitis.

Function[edit]

Meibum[edit]

Lipids[edit]

Lipids are the major components of meibum (also known as "meibomian gland secretions"). The term "meibum" was originally introduced by Nicolaides et al. in 1981.[2]

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.[3]

Currently, the most sensitive and informative approach to lipidomic analysis of meibum is mass spectrometry in combination with liquid chromatography.[4]

Proteins[edit]

In humans, more than 90 different proteins have been identified in meibomian gland secretions.[5]

Clinical significance[edit]

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.[6][7] Factors that contribute to MGD can include things such as a person's age and/or hormones.[8] Treatment can include warm compresses or expression of the gland by a professional. In some cases antibiotics or steroids are prescribed.

History[edit]

The glands are named after Heinrich Meibom (1638–1700), a German physician.

See also[edit]

References[edit]

  1. ^ "eye, human." Encyclopædia Britannica. Encyclopaedia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
  2. ^ Nicolaides N, Kaitaranta JK, Rawdah TN, Macy JI, Boswell FM 3rd, Smith RE. "Meibomian gland studies: comparison of steer and human lipids." Invest Ophthalmol Vis Sci. 1981 Apr;20(4):522-536. PMID 7194326.
  3. ^ Butovich IA (November 2009). "The Meibomian puzzle: combining pieces together". Prog Retin Eye Res 28 (6): 483–498. doi:10.1016/j.preteyeres.2009.07.002. PMC 2783885. PMID 19660571. 
  4. ^ Butovich IA. "Lipidomic analysis of human meibum using HPLC-MSn." Methods Mol Biol. 2009;579:221-246. PMID 19763478.
  5. ^ Tsai PS, Evans JE, Green KM, Sullivan RM, Schaumberg DA, Richards SM, Dana MR, Sullivan DA. "Proteomic analysis of human meibomian gland secretions." Br J Ophthalmol. 2006 March;90(3):372-7. doi:10.1136/bjo.2005.080846 PMID 16488965.
  6. ^ "Managing and Making Sense of MGD". Review of Ophtamology. 10-4-2012. Retrieved 26-2, 2014. 
  7. ^ "Rethinking Meibomian Gland Dysfunction: How to Spot It, Stage It and Treat It". American Academy of Ophthalmology. 2014. Retrieved February 26, 2014. 
  8. ^ "The Role of Meibomian Gland Dysfunction and Lid Wiper Epitheliopathy in Dry Eye Disease". American Academy of Optometry. 2012. Retrieved February 26, 2014. 

External links[edit]