An adequate and consistent layer of tears on the surface of the eye is essential to keep your eyes healthy, comfortable and seeing well.
- Tears bathe the eye’s surface to keep it moist and wash away dust, debris and microorganisms that could damage the cornea and lead to an eye infection.
A normal tear film consists of three important components:
1. An oily (lipid) component
2. A watery (aqueous) component
3. A mucous-like (mucin) component
- Each component of the tear film serves a critical purpose, for example: tear lipids help keep the tear film from evaporating too quickly and increase lubrication, while mucin helps anchor and spread the tears across the surface of the eye.
Each tear component is produced by different glands on or near the eye:
a. The oily component is produced by Meibomian glands in the eyelids.
b. The watery component is produced by lacrimal glands located behind the outer aspect of the upper eyelids.
c. The mucin component is produced by goblet cells in the conjunctiva that covers the white of the eye (sclera).
- A problem with any of these sources of tear film components can result in tear instability and dry eyes, and there are different categories of dry eyes, depending on which component is affected.
- For example, if the Meibomian glands don’t produce or secrete enough oil (Meibum), the tear film may evaporate too quickly. This is a condition called “evaporative dry eye.“
- The underlying condition “called Meibomian Gland Dysfunction”, is now recognized as a significant factorin many cases of dry eye syndrome.
In other cases, the primary cause of dry eye is a failure of the lacrimal glands to produce enough watery fluid (aqueous) to keep the eyes adequately moistened. This condition is called “Aqueous Deficiency Dry Eye.“
The specific type of dry eye often will determine the type of treatment your eye doctor recommends, in order to provide relief from dry eye symptoms.