What Is MGD?
MGD stands for Meibomian Gland Dysfunction. This condition is more often referred to as meibomitis, and also meibomianitis, and lid margin disease. It is also called posterior blepharitisin some texts. This phrase refers to the dysfunction and inflammation of meibomian (sebaceous) glands.
Where Are Meibomian Glands Located?
About 50 of these sebaceous glands are located along the edge of the upper eyelid and 25 of them in the lower eyelid. The number of meibomian glands has been reported differently in different sources. These glands are responsible for the secretion of sebum, an oilyfluid, which prevents tear evaporation.
In general, different layers of tear film include:
1. The innermost and thinnest layer, a thin layer of mucus, is produced and secreted by some cells in the conjunctiva.
2. The middle layer is the thickest layer and is,in fact, similar to a very dilute solution of water and salt. The major lacrimal gland, located under the upper eyelid, along with accessory glands produce this layer of tear. This layer keeps the eye moist, and on the other hand, removes debris and foreignbodies from the eye. The problem with the secretion of this aqueous layer of the eye is the most common cause of dry eye, which is referred to as keratoconjunctivitissicca.
3. The outermost layer of tear film is a very thin oily layer and is secreted by meibomian glands. The main function of this layer is to prevent the evaporation from its underlying aqueous layers.
What Is the Function of Meibomian Glands?
As noted above, the secretion of meibomian glands helps maintain the stability of the lacrimal fluid in the eye and, as a result, moisturize the eye. By blinking, the downward action of the upper eyelid pushes on lipids and pulls up a layer of them, which causes the tear to be covered by lipids and prevents its evaporation, and thus the eye stays moist.
What Happens During the Dysfunction of These Glands?
Dysfunction of these glands causes tears to evaporate more rapidly, resulting in symptoms such as dry eyes, burning eyes, irritation, foreign body sensation and redness in the eyelids and conjunctiva. People who use contact lensesmay express that they can no longer tolerate wearing them as before.
What Causes Meibomian Gland Dysfunction?
The major reason for the dysfunction of these glands is their obstruction, which is commonly caused by hormonal changes. Changes in the levels of estrogen result in the thickening of the secretions. Meanwhile, the change in estrogen levels increases the number of staphylococci, which are naturally part of the microbial ocular surface.
The two skin disorders that can cause posterior blepharitis (or MGD) are rosacea and seborrheic dermatitis(dandruff).
What Are the Differential Diagnosis of MGD?
Dry eye syndrome: Many patients suffering from dry eyes are often treated as patients with aqueous deficiency on the ocular surface, and use artificial tear drops. Meibomian gland dysfunction in its early stages is not usually included in differential diagnosis.
Anterior blepharitis: Chronic blepharitis can cause chronic meibomian gland dysfunction, which ultimately results in dry eyes.
What Is the Treatment of This Dysfunction?
The basis of the blepharitis treatment (either anterior or posterior) is a long-term commitment to an eyelid hygieneprogram. Eyelid Hygiene Tips:
1-Using warm compress which results in melting solid plaques on the eyelid margin.
2-The edges of the eyelid should be washed and cleaned in order to remove coagulated material from the eyelid margin and wash pores of meibomian glands. Usually, water is used for this purpose. However, some physicians prefer to use a few drops of baby shampoo. It should be noted to only clean the eyelid margin in the process, and not to damage the adjacent conjunctiva and skin. Extreme washing is forbidden and may even damage the eye.
Drug Therapy:
1. Applying a topical antibiotic to the eyelid margin after washing up or using warm compress on it. Typically tetracycline is used for 1 to 2 months.
2. In drugtherapy of blepharitis, not only topical antibiotics but also topical corticosteroids and oral antibiotics are used.
3. Recently, articles have been published on the effectiveness of using omega-3 fatty acids in the form of pills, for treating blepharitis and dry eyes.