DRY EYES

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Dry eyes, or the Dry Eye Syndrome (DES), is one of the most common eye conditions, and while it has a demographic propensity, on some level nearly everybody suffers from dry eyes at one time or another.

 

The phenomenon of dry eyes is so common that many people simply accept it and suffer through it without investigating its causes and treatments. Many explanations for dry eyes can be identified and addressed, making the dry eye sufferer more comfortable and better sighted. Some underlying causes, like Meibomian Gland Dysfunction, can be treated in order to arrest or postpone the progression of the disease.

 

 

TEAR FILM PHYSIOLOGY

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It is helpful to be familiar with the composition of the tear film to better understand dry eyes. 

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

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• OIL:  The lipid layer is the outer most portion of the tear film. This layer is produced by the Meibomian glands of the eyelids. An inadequate oil layer results in premature evaporation or break-up of the tear film. That is why people with dry eyes will often tear inappropriately.

• AQUEOUS: The aqueous layer comprises 90% of the tear film and provides its 'cushion'.  This layer is produced by the lacrimal gland located under the upper lid.  Without a proper aqueous layer there is a relative excess of mucus and oil, leaving the eye dry with strands of mucus accumulating in the corners 

• MUCUS:  The mucus layer is formed by the goblet cells in the conjunctiva. The mucus helps the tear film to adhere to the eye.  

 

These three 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 even if there is an abundance of tears produced.

 

SYMPTOMS OF DRY EYES

 

• blurred vision

• fluctuation in vision

• foreign body sensation 

• intolerance to lights

• "halo" at night

• redness

• irritation

• crusting of the eyelids

 

In addition, stys, known as chalazia may result from chronically blocked oil glands that continue to secrete their oil.

 

TEAR FILM PATHOLOGY

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As previously stated, the defect in the tear film will result in specific symptoms:

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• MUCUS:  Reduced mucus production is relatively uncommon. Chemical injury to the eye can lead to this form of damage. An inadequate or absent mucus layer does not allow the tears to adhere to the corneal surface. As a result, the eye will develop xerophthalmia which can lead to corneal ulceration and scarring.

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• AQUEOUS: Aqueous production diminishes with age and is impacted by hormones, Therefore, peri- and post-menopausal women will typically see a substantial decline in the aqueous layer. A reduced aqueous layer renders the eyes more sensitive to environmental challenges and allows the disproportionate abundance of mucus to create stringy, or 'ropey' secretions.

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• OIL:  While only 5% of the tear film, the oil layer is the most superficial layer and prevents premature evaporation of the tear film.  Lid irregularities, skin conditions that affect the oil glands (for example acne rosacea), medications that cause dryness and environmental factors can compromise oil production. This may lead to stys (chalazia) from sludging of the oil, scaling around the eyelids and eyelashes (blepharitis), or premature break-up of the tear film with foreign body sensation, blurred vision, redness and light sensitivity.

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To learn more about the treatment of DRY EYES, click here:  

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