DRY EYES, aka, MEIBMOIAN GLAND DYSFUNCTION (MGD)

DRY EYES

Dry eyes are among the most universal eye diseases, and while not always the most serious, they are among the most dreadful. 

On some level nearly everybody suffers from dry eyes at one time or another, but women, particularly women as they enter or pass through menopause,  experience some degree of eye dryness. While this is usually folded into "the way things are", this condition can be distracting to some, and absolutely disabling to others.

 

The phenomenon of DRY EYES is so common that many people accept it and suffer through it without attending to its many causes and possible interventions.  While not all dry eyes can be improved, many causes for dry eyes can be identified and addressed, making the dry eye sufferer more comfortable and better sighted. Perhaps more importantly, some entities that cause dry eyes, like MEIBOMIAN GLAND DYSFUNCTION, can be treated in order to arrest or postpone the progression of the disease.

TEAR FILM PHYSIOLOGY

To better understand the pathology of dry eyes, it is helpful to recognize the makeup of the tear film.  The components of the tear film and the functions that they serve are directly related to the signs and symptoms that can be seen in their absence and impact the therapeutic approaches to "Dry Eyes". 

 

The tear film has three basic components that form distinct layers of the tear film:

 


 

  • OIL:  The oil layer, also known as the lipid  layer is the outer most portion of the tear film. This layer is produced by the Meibomian glands of the eyelids and is secreted by virtue of a proper blink. An inadequate oil layer results in premature evaporation or break-up of the tear film.

  • AQUEOUS: The aqueous layer comprises 90% of the tear film and provides the 'cushion' of the tear film.  This layer is produced by the lacrimal gland under the upper outer lid.  Without a proper aqueous layer there is a relative excess of mucus and oil and a thin, ineffective tear film 

  • MUCUS:  The mucus layer is formed by the goblet cells on the sclera (the white of the eye) and create the layer of the tear film that is in direct conact with the eyeball. This layer enables the tear film to adhere to the eye surface.  Without a proper mucus layer the tear film will not remain evenly on the eye surface.

These three, seemingly ordinary components, need to be produced and blend efficiently with each blink. Without their cohesive presence, a person will experience signs and symptoms of DRY EYES. These may include:

 

  • blurred vision

  • fluctuation in vision

  • foreign body sensation

 

 

 

  • intolerance to lights

  • "halo" at night

  • redness

  • irritation

 

  • crusting of the eyelids

  • "sleep" or crust in the eye upon awakening

 

Chalazia (sing: Chalazion) may result from chronically blocked oil glands that continue to secrete their oil. The gland becomes congested and may even trap skin bacteria and become infected (cellulitis)

TEAR FILM PATHOLOGY

Defects in any of the tear film layers will create disease that is typical of the particular layer in the tear film:

 

  • MUCUS:  Reduced mucus production is relatively uncommon. Mucus is produced by "goblet cells on the eye surface that can be damaged by chemical injury.  Acid or lye burns are typical injuries that can lead to this form of damage.

With an inadequate or absent mucus layer, the tear film cannot adhere to the corneal surface. As a result, the eye will develop xerophthalmia which can lead to corneal ulceration and scarring.

  • AQUEOUS: Aqueous production dimishes naturally with age,and is profoundly impacted by hormones, Therefore, peri- and post-menopausal women will typically see a substantial decline in the aqueous layer. This layer comprises 90% of the tear film

A reduced aqueous layer renders the eyes more sensitive to environmental challenges and allows the disporpotionate abundance of mucus to create stringy, or 'ropey' secretions.

  • OIL:  The oil layer, like the mucus layer, makes up only 5% of the tear film, but is the most superficial layer and therefore, protects the ocula surface from premature evaporation. The oil is prodiced in the Meibomian glands of the eyelids; virtually each lash is the orifice of a Meibomian gland.  Lid irregularities, skin conditions that affect the oil glands (for example acne rosacea), medications that cause dryness and environmentl factors can compromise oil production.

When oil production is not optimum, people may get stys from sludging of the oil, scaling around the eyelids and eyelashes, as in eczema and seborrhea, or, premature break up of the tear film with foreign body sensation, blurred vision, redness and light sensitivity.

External Hordeolum (chalazion)

There is a visible 'white head' at the apex of this chalazion suggesting that its content may be pliable and able to squeeze out