Dry Eye and Tear Film Insufficiency
What are Tears?
The secretion of tears is generally a response to an irritation of the eye, other than those shed in times of joy or sorrow, of course. Tears consist of a salty liquid that moistens the eyes and inner eyelids. The flow of tears exceeds the boundaries of the eyelids when overproduced in a compensatory response to irritation or most commonly when one cries. In addition to protecting and nourishing the eye, tears also refract or bend light to help you see clear, sharp images.
There are three types of tears: Emotional, Reflex and Basal tears.
As we all know, emotional tears flow in response to strong emotions, whether joyous or sorrowful, aggravation or pain. Reflex tears are produced as a response to eye irritation in an effort to wash away the irritant. They are also released in response to other stimuli, such as spicy foods, sudden bright light or involuntary bodily functions like yawning, vomiting or extended coughing.
Tears that flow in response to irritation or emotion have a different formation than basal tears, which are for protection and lubrication. You may have noticed this difference in that after crying your eyes hurt or burn. Excessive tearing in this manner can dilute the tear film, leaving the eye feeling less lubricated.
Not as commonly known, but extremely important to the eye are basal tears. The term basal tears refers to the protective tear film that normally covers the eye surface. The quality and composition of which will greatly affect optimal eye health, comfort and clarity of vision. In addition to moistening the eye, basal tears help wash away dust or debris, and prevent microscopic organisms from causing an eye infection.
The tear film consists of three distinct layers and their unique roles:
- Lipid (oily) layer – keeps the film from evaporating too fast and increases lubrication
- Aqueous (watery) layer – helps spread the tear film and protects against infectious organisms
- Mucous (mucus) layer – anchors the tear film to the eye and helps with even distribution
Tear Film Insufficiency and Dry Eye Disease
An imbalance or dysfunction of any of these components can lead to tear film insufficiency, resulting in Dry Eye Disease. The precise cause of which depends on the affected layer(s). For example, if meibomian gland secretion is disrupted either in production or flow of oil, it can cause the tear film to evaporate too quickly, resulting in the dry eye condition known as “evaporative dry eye.” The underlying cause of which is Meibomian Gland Dysfunction (MGD), the leading cause of dry eye. (For more information on MGD, click here.)
Another underlying cause of dry eye syndrome is “aqueous deficiency dry eye.” As the name indicates, it affects the aqueous layer of the tear film. In this case, the lacrimal glands are not producing or adequately releasing enough fluid to maintain this layer, affecting the overall tear film composition. Additionally, there are patterns and structures of the mucins which affect the normal anchoring and tear film distribution of the mucous layer.
Resolving dry eye associated with tear film insufficiency is not a matter of simply making the eyes “wetter.” Rather, the underlying issue causing the disruption of basal tears needs to be addressed to achieve optimal eye comfort and health.
If you are suffering from dry eye symptoms, contact Eyes For Life to schedule your evaluation with one of our Dry Eye Specialists or for more information about our Dry Eye Relief Management.