Tears are much more than just water. Tears are composed of 3 major components or layers:
o Inner Mucus Layer – is produced by cells found on the surface of the eye. This layer helps the middle watery layer to stick to the eye and spread evenly over the surface.
o Middle Watery Layer – is produced by the lacrimal gland. In addition to water, this layer is made up of proteins, electrolytes, and vitamins that are critical in keeping the surface of the eye healthy.
o Outer Oily Layer – is produced by the glands located near the base of our lashes. A smooth oil layer helps prevent the water layer from evaporating.
A deficiency in any one or more of these layers can result in dry eye