PretectalOcular surface / Visual explainer
Inside the tear film
A blink spreads tears across the eye. Select each component to explore the job it does.
A teaching view of the tear film
Components shown separately for clarity. Not to scale.
The outer oil component
Helps slow evaporation
The oily surface helps keep tears from drying out too quickly and contributes to a smooth optical surface.
Imagine this protective surface becoming uneven. Water alone cannot do every job in the tear film.
The idea to take away
Tear-film stability depends on more than water alone. Oils, water, and mucins have complementary roles at the eye's surface.
About this model
The three-layer view is a teaching simplification. The real tear film is dynamic, and its components interact. Layer thicknesses are not to scale. This explainer does not diagnose the cause of dry eye.
Which component helps slow tear evaporation?
Go to the source
References checked October 1, 2026How Tears Work
National Eye Institute
A plain-language explanation of the tear film and its functions.