3 Layers of Tear Film: Understanding the Cause of Dry Eyes - CARiNG Pharmacy

3 Layers of Tear Film: Understanding the Cause of Dry Eyes

Experiencing burning in the eyes? Feeling a scratchy sensation in the eyes?
Those might be symptoms of dry eyes.

Dry eye diseases can be caused by a range of conditions that affect the tear film. This is why understanding the structure of the tear film is the key to understanding dry eye diseases.1

3 Layers of Tear Film

Any problems that disrupt the integrity of the tear film will cause dry eyes. Our tear film is made up of mucin layer, aqueous (water) layer and lipid (oil) layer.1

Lipid Layer

The outermost layer of the tear film, the lipid layer, functions to stabilize the tear film.2 The lipid layer protects the water in the eye from evaporating too fast.

Aqueous Layer

The aqueous layer is the largest part of the tear film.2 This layer functions to nourish and protect the eye. Other than keeping the eye hydrated, the aqueous layer also helps to supply oxygen and nutrients to the cornea.3

Mucin Layer

The mucin layer allows the aqueous layer to adhere to the otherwise water repelling cornea.

Major Types of Dry Eye Diseases

There are two main types of dry eye diseases, namely aqueous deficient dry eyes and evaporative dry eyes.4

Aqueous Deficient Dry Eyes (Decreased Tear Production)

In this condition, the eyes are unable to produce sufficient levels of water. This can be caused by:1

  1. Aging
  2. Medical conditions such as Thyroid disorders and Vitamin A deficiency 
  3. Medications such as antihistamines or certain antidepressants

Evaporative Dry Eyes (Increased Tear Evaporation) 

Meibomian gland is responsible for the secretion of the oils in the lipid layer. Dysfunctional meibomian gland results in increased tear evaporation.4

What Can You Do to Reduce the Risk of Dry Eyes?

Try paying more attention to all of the following tips to reduce the risk of being troubled by dry eye diseases:1

1. Avoid air blowing in your eyes:
This increases the evaporation rate of the tear film.

2. Take eye breaks during long tasks
You can rest your eyes by closing your eyes or blink repeatedly for a few seconds. This helps to spread the tears evenly across the eye.

3. Position the computer below eye level
Looking at a computer screen above eye level forces the eye to open larger. This increases the evaporation of our tears.

4. Stop Smoking
Cigarette smoke contains various chemicals that irritate the eye.

5. Use artificial tears regularly
Using an eye drop frequently helps to keep the eye moisturised.

You may ask: ‘What else can I do? What vitamins can I take for my dry eye problem? What artificial tears suit me best?’
If you have any such questions regarding dry eyes, remember to ask your CARiNG pharmacist!

References: 

  1. Dry eyes – Symptoms and causes [Internet]. Mayo Clinic. 2022 [cited 20 August 2022]. Available from: https://www.mayoclinic.org/diseases-conditions/dry-eyes/symptoms-causes/syc-20371863#:~:text=Tear%20glands%20and%20tear%20ducts,-The%20tear%20glands&text=Dry%20eyes%20are%20caused%20by,layers%20can%20cause%20dry%20eyes.
  2. Understand dry eye – What are tears? | systane.com [Internet]. Systane-ca.myalcon.com. 2022 [cited 20 August 2022]. Available from: https://systane-ca.myalcon.com/ca-en/eye-care/systane/dry-eyes/what-are-tears/
  3. The role of the tear film [Internet]. Vismed.trbchemedica.co.uk. 2022 [cited 20 August 2022]. Available from: https://vismed.trbchemedica.co.uk/business-professionals/understanding-the-tear-film/the-role-of-the-tear-film
  4. Dry Eye Disease (Keratoconjunctivitis Sicca): Practice Essentials, Background, Anatomy [Internet]. Emedicine.medscape.com. 2022 [cited 20 August 2022]. Available from: https://emedicine.medscape.com/article/1210417-overview#a4