Tear film

Tears produce corneal tear film, which generally has a thickness from 0.005 to 0.012 mm and is renewed every 10 to 30 seconds. Its function is to keep the cornea smooth and shiny, protecting it from irritation, foreign bodies and participate in the metabolism of the cornea.

The tear film is composed of three layers: an inner mucosal (contains mucin) middle aqueous layer (containing enzymes, proteins, antibodies) and an outer lipid layer.