Tear film and eyelids
TEAR FILM AND EYELIDS
TEAR FILM
The tear film is traditionally described as having three layers:
- The outer lipid layer
- The middle aqueous layer
- The mucous layer, which borders on the cornea
The lipid layer is the superficial oily layer of the tear film that is in direct contact with ambient air. These lipids are mainly secreted by the meibomian glands.
EYELIDS AND GLANDS
The eyelids contain numerous oil-producing meibomian glands, located in rows within the tarsal plate near the lashes.
The force of each blink causes oil to be excreted from the meibomian glands onto the lid margin. This oil helps to prevent evaporation of the tear film.
Any dysfunction of these glands will affect the tear film and make it less stable; this is the main reason people have dry eye symptoms.
