Tear film, structure and function

Abstract

A vestige of the evolving forms of aquatic life to terrestrial life is the lacrimal system and its main function is to prevent dryness of the anterior segment of the eye to allow their operation in the Earth’s environment. The product of this system is already in tears and the 5th century BC, Hippocrates recognized its importance. This thin film is very versatile and has great ability to adapt to the changing environment, but when conditions are adverse, it may become fragile and reduce its functionality exposing the eye to potential damage. Understanding the structure of the tear film is necessary to differentiate its normal operation of the anomalous, which would lead to a more accurate diagnosis of the lacrimal alterations. It detailed the parties for the meniscus fringe of the eyelids and tear film itself, given its importance in the integrity and corneal eye. The objective of this thematic review is to describe different theories proposals on the structure and functions of the tear film, as the foundation for the understanding of their clinical performance.