Abstract:

As a component of the ocular surface microenvironment, tear film plays an important role in the development of ocular surface diseases. The stimulation of endogenous factors and exogenous factors can alter the composition of the tear film that ultimately cause the instability of the tear film, which will even act as an initial factor in ocular surface diseases, changing the morphology and function of other components of the ocular surface microenvironment. Cornea, conjunctiva and even the nerve and microbiota on the ocular surface will change. The factors that can destroy the homeostasis of the tear film can be divided into endogenous factors and exogenous factors. Endogenous factors include the destruction of tear secretion tissues, abnormal ocular surface structure, disorder of ocular surface microbiota, and abnormalities in the homeostasis of the body. The exogenous factor is the stimulation and destruction from outside that can affect the tear film. (Int Rev Ophthalmol, 2019, 43:   337\|340)