From 6 to 20 % of adults over 40 years have some symptoms referred to a kind of tear dysfunction a condition which is linked to a series of persistent symptoms, The origin of this disease is multifactorial and linked to pathological conditions of one of the portions of the Eye Surface System, which includes tear film, cornea, conjunctiva, accessorial tear glands, Meibomian’s glands, mucus-epidermal junction, the main tear glands and the systems of nerve connection, excretory ducts and nasolacrimal sac. Every form of tear dysfunctions, induces a loss of adaptation capacity of the system of ocular surface. They may be linked to epithelium malfunctioning phenomena and to less evident phenomena of inflammation but a typical aspect is always present: the instability of tear film with loss of its crucial architecture.
The tear film is a dynamic and essential part of the “system of ocular surface” and it interacts in a simultaneous way with every other component, this has to be kept in mind in planning the therapeutic approach toward this disease. The formulation of a tear substitute must aim to a complete restoration of film structure thanks to the mixture of components able to correct the evaporative stress and at the same time to give stability, volume, adhesiveness and elasticity to tear film for a long time, to protect the epithelium of the ocular surface, to defuse the negative effects of biological detritus and pro-inflammatory agents and to reduce the symptoms of physical and visual discomfort. Since the principal point of this disease is the instability of the film, the restoration of a stable architecture is the first step for the rehabilitation of ocular surface and it is a step that cannot be renounced.