Tear film
Tear Film
The Tear Film (pronunciation: /tɪər fɪlm/) is a thin layer of fluid that covers the surface of the Cornea and Conjunctiva in the Eye. It serves to lubricate, nourish, and protect the eye.
Etymology
The term "Tear Film" is derived from the English words "tear," meaning a drop of clear salty liquid secreted from glands in the eyes, and "film," referring to a thin layer or coating.
Composition
The Tear Film is composed of three layers: the Lipid Layer, the Aqueous Layer, and the Mucin Layer. Each layer is produced by different glands in the eye and has a specific function.
- The Lipid Layer is the outermost layer, produced by the Meibomian Glands. It prevents the tear film from evaporating and helps maintain its stability.
- The Aqueous Layer is the middle layer, produced by the Lacrimal Glands. It provides hydration, nutrients, and oxygen to the cornea.
- The Mucin Layer is the innermost layer, produced by the Goblet Cells in the conjunctiva. It helps the tear film adhere to the eye.
Function
The Tear Film plays a crucial role in maintaining the health and function of the eye. It provides lubrication to prevent friction when blinking, nourishment to the cornea, and protection against foreign particles and pathogens. It also contributes to clear vision by creating a smooth refractive surface on the cornea.
Related Terms
- Dry Eye Syndrome: A condition characterized by a deficiency in the quality or quantity of the tear film, leading to discomfort and visual disturbances.
- Blepharitis: An inflammation of the eyelids, often associated with dysfunction of the Meibomian Glands, affecting the lipid layer of the tear film.
- Keratoconjunctivitis Sicca: Also known as dry eye syndrome, it is a condition where the eyes do not produce enough tears or the tears evaporate too quickly.
External links
- Medical encyclopedia article on Tear film
- Wikipedia's article - Tear film
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