function of each tear film layer
The tear film consists of three layers: An oily layer. A watery layer. A layer of mucus. Each layer has its own purpose. The oily layer, produced by the meibomian glands, forms the outermost surface of the tear film. Its main purpose is to smooth the tear surface and reduce evaporation of tears. The middle watery layer makes up most of what we ordinarily think of as tears.
Traditionally, the tear film has been described as having three distinct layers: 1  an outermost lipid (oily) layer. 2  an aqueous (watery) layer that makes up 90% of the tear film volume; and. 3  a mucin layer that coats the corneal surface.
It contains water and proteins and is secreted by small glands in the conjunctiva and the larger lacrimal gland. The aqueous layer makes up the majority of the tear volume and is responsible for tear spreading. Mucous Layer: The mucous layer works as an anchor to hold the tear film to the eye.