What is dry eye disease?



The term dry-eye disease, or dry eye syndrome (DES), refers to a number of different conditions, all of which are characterized by inadequate lubrication of the surface of the eye.


Dry eye disease can be caused by a dysfunction in one or more components of tear production anatomy


The diagram below shows tear production. The acqueous component of tears are secreted by the lacrimal gland. The lipid component of tears is secreted by the meibomian glands. Healthy tears need both of these components and deficiencies in either one can cause drye eye and other ocular surface disease. When we diagnose dry eye disease, we determine whether the tears are deficient in the aqueous component or the lipid component and target treatments accordingly. Tears are then drained from through lacrimal punctum. Too much drainage can also try out the eyes. One way to correct excessive drainage is to install punctal plugs to slow the drainage in an in-office procedure.


Tear production and drainage - medical diagram showing lacrimal gland, punctum, lacrimal canal, meibomian gland, lacrimal ducts - Perspective Optometry Vancouver


Tear film deficiencies


Usually inadequate lubrication of the ocular surface is caused by a deficiency of one or more of the tear-film layers (there are three of them: the aqueous, the mucin and the lipid layer). There are two glands involved the production and regulation of tears. The lacrimal gland is responsible for tear production and the meibomian gland is responsible for the lipid layer which is critical for the stability of the tear film. If these glands are are not working properly, the eyes dry out.


Symptoms of dry eye disease


The most common complaints are ocular discomfort and visual fluctuations. Dry eye can arise due to a variety of underlying processes but inflammation is a common denominator in dry eye disease, which can further damage the epithelium of the cornea and its underlying structures.


Surprisingly, dry eye syndrome can also lead to excessively watery eyes due to tears lacking the proper balance of mucous, water, and oil to coat the eyes properly. Chronic dry eye can lead to damage of the eye’s surface, an increased risk of eye infections, and eventually, the inability to produce tears. Left untreated, severe forms of dry eye can even damage your vision.


The symptoms of dry eye vary from patient to patient. Most patients have mild to moderate symptoms, including eye discomfort, the feeling that there is something in their eye, burning, stinging, grittiness, light sensitivity, blurring, tired eyes (visual fatigue) and the inability to continue to wear contact lenses. In some patients, symptoms are debilitating.


What causes dry eye disease?


Dry-eye can be caused by certain drugs, eyelid problems or defects in the epithelial cell's of the cornea (the clear surface of the eye) that are caused by infection or trauma. Dry eye can also be associated with systemic diseases such as Sjögren's syndrome.


Gland dysfunction is a common cause of dry eye syndrome


The dysfunctioning or atrophy of the glands that produces the components of tear film is a common cause of dry eye diease. It is estimated that 86% of dry eye suffers have meibomian gland dysfunction. The images below were taken by LipiScan, an in-office imaging procedure we use to examine the quality of a patient's meibomian glands. Some patients experience gland drop out or atrophy as shown in the image; when this happens, they do not produce enough of the lipid component of tear film causing excessive tear evaporation. We use LipiFlow to obtain maximimum tear production from the remaining glands.


86 percent of dry eye sufferers have meibomian gland dysfunciton - LipiScan images showing gland truncation and gland drop out - Perspective Optometry Vancouver


The environment and computer use can also contribute to dry eyes.


LASIK can cause dry eye syndrome

Sometimes the defects in the epithelial cells of the cornea that cause dry eye are a side effect of LASIK surgery. Dry eyes are extremely common after LASIK. It is thought that LASIK damages the nerves in the cornea making it difficult for them to tell the brain that its time to produce more tears.


Certain medications can cause dry eye syndrome


Certain medications can dry your eyes or make dry eye syndrome worse. Here is a short list of common medications that are linked with dry eye syndrome:


  1. Birth control pills
  2. Antibiotics
  3. Pain Relievers
  4. Decongestants
  5. Beta Blockers
  6. Anti Depressants
  7. Artificial tears:  It is common for over the counter commercial eye drops to make dry eye worse.  That is why it is important to have your doctor test your eyes and your tears to determine which drop is best for you. 
  8. Acne medication



How common is dry eye disease?


Dry eye syndrome is one of the main reasons that patients visit eye doctors in North America. It is difficult to determine the prevalence of dry eye syndrome because different studies use different criteria for diagnosing the syndrome. Determining the prevalence of DES is complicated by the lack of a gold standard for diagnosis; moreover, each study seems to use different criteria.


Based on a number of different studies, the prevalence of dry eye syndrome is anywhere from 6.7 percent to 28.7 percent. Women are 1.5 to three times more likely than men to have dry eye disease. The group that is most at risk of dry eye disease is post-menopausal women and women with premature ovarian failure. There is also an increased risk of dry eye syndrome in pregnant and lactating women.


Various treatment modalities are available to address the need for lubrication of the ocular surface, inflammation, and gland dysunction.

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