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Tear film

Updated: Jul 18, 2022

The tear film of the eye is a thin layer of tears that moistens the front part of the eye. The tear film has an optical function for the eye and a protective function. The protective function is to flush foreign bodies out of the eye and the tear film acts as a lubricant to allow the eyelids to glide smoothly over the surface of the eye. In addition, the tear film contains important enzymes which play a major role in the defense against infections. The diffusion of oxygen for the supply of the cornea is also achieved via the tear film of the eye. The different functions of the tear film are achieved by different components of the tear secretion. The individual components of the tear film are produced in glands which are located in different places of the conjunctiva, the eyelids and at the upper edge of the eye socket. The secretions of the tear sources are not distributed in a homogeneous mixture, but condense in different layers of the tear film.

Different layers of the tear film

The tear film is divided into three layers. The tear film has a total thickness of a fraction of a millimeter and consists of a lipid layer, an aqueous layer and a mucus layer which rests on the uppermost corneal layer. The uppermost phase is the fat layer facing the air, which prevents the tear film from evaporating too quickly. Numerous organic and inorganic substances are dissolved in the middle aqueous phase. The aqueous phase is the thickest layer and in the area of the cornea it changes into a mucus layer which compensates for irregularities of the cornea. The interaction of the layers allows a functional tear film to form. Inadequate secretion of tear fluid can affect the quantity and composition of tears and leads to an obstruction of corneal metabolism.

Tear film and contact lenses

Contact lenses are worn during the aqueous phase of the eye's tear film. InnoVision's innovative contact lens design ensures that the tear film remains functional. In particular, the design of the edges of the contact lens and an aspherical shaped back of the contact lens supports the smooth circulation of the tear film and oxygen supply to the eye.

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