Types of Dry Eye

Dry Eye Disease comes in different forms.  There are two main types:

1.  Evaporative Dry Eye  :  usually due to problems with the Meibomian glands

2. Aqueous Tear-Deficient Dry Eye  : due to problems with the lacrimal glands


The two types can co-exist i.e. you can have both types together.  Generally though, one of the two types is more dominant in any one individuals eyes.


Evaporative Dry Eye

Evaporative Dry Eye is the more common type and accounts for 65% of Dry Eyes.

It is caused by problems with the eyes own natural oils that are in the tear film.   In Evaporative Dry Eye, there is either too little, too much or poor quality oil in the tears. The function of the oils is to stop the tears from evaporating away quickly.  When the oil is compromised, the tears  don't stay on the surface of the eye as long as they should, hence leading to exposed areas and feelings of dryness. 

The problems with the oil occur as a result of Meibomian Gland Dysfunction (MGD). The Meibomian Glands are oil producing glands in the eyelids that normally produce a thin clear oil that is expressed into the tear film when we blink. When the glands are not working properly, the oil produced can be poor quality or additionally either too much or too little oil may be being expressed into the tears. 

Click on the highlighted text to read more on Meibomian Gland Dysfunction 


Aqueous Tear-Deficient Dry Eye

Aqueous forms the watery parts of the tears.  Aqueous is produced by the lacrimal glands in the upper eyelids. A deficiency of aqueous in the tears is one of the conditions that can cause dry eye syndrome.

Dryness due to Aqueous Deficiency / Lacrimal Gland Dysfunction is much less common than dryness due to oil (lipid) problems / Meibomian Gland Dysfunction.  

Reduction in Aqueous  production can be due to a number of causes, such as certain auto-immune conditions like Sjoergens or Rhuematoid Arthritis, some medications and laser eye surgery.


Treatment of Evaporative & Aqueous Deficient Dry Eye

The treatment of the two types of Dry Eye is quite different from one another.  That's why for optimally successful treatment of Dry Eye Syndrome a careful evaluation should be done to establish the type of Dry Eye present.  The wrong treatment is either ineffective, or it can even make the symptoms worse.




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