Meibomian gland

Evaporative dysfunction is caused by a reduction in the lipid layer of the tear film. Most often, this condition is caused by MGD or blepharitis. MGD is traditionally conceptualized as a triad of meibomianitis (stagnated secretions within the meibomian glands), meibomian seborrhea (overabundance of meibomian secretions into the tear film), and seborrheic blepharitis (oily debris visible on the eyelashes and ocular adnexal surfeces). Additionally, we have become increasingly aware of the influence of male hormones, or androgens, on the health of the meibomian glands. Clinically significant androgen deficiency, which naturally occurs in women of menopausal age and men in... 

Mancini M., Majumder D., Chatteijee B. and Roy A.K. (1989). a2p.-Globulin in modified sebaceous glands with pheromonal functions localisation of mRNA and protein in preputial, Meibomian and perianal glands. J Histochem Cytochem 37, 148-157. 

Nicolaides, N., et al. 1981. Meibomian gland studies Comparison of steer and human lipids. Invest Ophthalmol Vis Sci 20 522. 

Penicillins resistant to penicillinase can be used to treat ocular infections. An internal hordeolum, which is an infection of a meibomian gland typically with staphylococci, can be treated with oral dicloxacillin when the hordeolum is severe or not resolving with more conservative treatment. 

Dry eye results from an unstable tear film or tear evaporation, which results in damage to the ocular surface. The Unified Theory published in 1998 provided the basis for understanding dry eye as an inflammatory disease of the integrated lacrimal functional unit.The lacrimal functional unit consists of the ocular surface (cornea, meibomian glands, and conjunctiva), main and accessory lacrimal glands, and their interconnecting nerves. In the healthy state the lacrimal functional unit maintains a... 

Perry HD, Doshi-Carnevale S, Donnenfeld ED, et al. Efficacy of commerciaUy available topical cyclosporine A 0.05% in the treatment of meibomian gland dysfunction. Cornea 2006 25 171-175. 

Positioned at the interface between the air and tear film, the lipid layer is produced by the meibomian glands with contributions from the glands of Zeis and Moll. Most of this layer consists of low-polarity lipids, such as wax and cholesterol esters, with traces of triglycerides. A thin polar portion, adjacent to the tear-aqueous layer, may contain surfactant phospholipids needed to spread lipid film over aqueous layers. The main purpose of the lipid layer appears to be to reduce evaporation of the tear film. 

A significant positive correlation has been observed between the levels of inflammatory cytokines in the conjunctival epithelium and the severity of ocular irritation symptoms and corneal fluorescein staining. The inflammatory cytokines and other inflammatory mediators also correlate positively to severity of conjimctival squamous metaplasia in Sjogren patients. These proin-flammatory cytokines also have been implicated in regulation of epithelial mucin expression, with several studies suggesting inflammation is central to the pathogenesis of meibomian gland dysfunction as well. 

The goals of OSD treatment are to relieve symptoms, heal the ocular surface, and prevent serious complications. Treatment of dry eye generally Ms into one of three categories—tear supplementation, tear conservation, or tear stimulation—in an attempt to reestablish the tear film quantitatively and qualitatively (Box 14-1). When possible, it is important to diagnose and treat coexistent or ancillary conditions that provoke or aggravate dry eye (e.g., blepharitis, meibomian gland disease, eyelid abnormalities). 

Cermak JM, Krenzer KL, Sullivan RM, et al. Is complete androgen insensitivity syndrome associated with alterations in the meibomian gland and ocular surface Cornea 2003 22 516-521. 

Mixed seborrheic-staphylococcal blepharitis Posterior lid margin Meibomian gland dysfunction Meibomian seborrhea Meibomitis Primary Secondary... 

Etiology. Meibomian gland secretions are responsible for the lipid component of the precorneal tear film. The chemical composition of meibum and/or the lipase action of the normal lid bacteria is thought to contribute to or cause blepharitis and in many cases the dry eye that accompanies it. The composition of meibum has been found to be different in normal and blepharitis patients, and there is a distinct difference between the types of MGD as well. Most studies of lid flora in bacterial blepharitis cases did not find any appreciable isolates from meibum that were not found as normal flora on the lids, therefore disproving the theory that the meibomian glands act as a bacterial reservoir. 

Signs of meibomitis include inspissated orifices of the meibomian glands (Figure 23-8A), cloudy or thickened yellow-white meibomian secretions on gland expression, frothy tear film (Figure 23-85), hyperemia, mild papillary conjunctivitis, and thickened rounded eyelid margins. SPK of the cornea and conjunctiva in the inter-palpebral space is associated with an unstable tear film evidenced by a markedly reduced tear breakup time. 

Management. The most effective treatment for MGD involves relieving any obstruction of the meibomian ducts and orifices by digital massage and gland expression two... 

Hordeola are extremely common typically self-limiting infections of the meibomian glands or the glands of Zeis and Moll.There are two distinct clinical types of hordeola defined by the glands involved, either external or internal. 

An internal hordeolum is a localized staphylococcal infection of the meibomian glands. The infection may result from blockage of the gland and is foimd more frequently in the upper lid. A specific change in meibomian gland secretion has been linked to internal hordeolum formation. 

Distichiasis can be an acquired or, rarely a congenital condition in which there is an accessory row of eyelashes emanating from the meibomian gland orifices. When congenital, it may occur sporadically or may be autosomal dominant. 

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