Tranenfilms

Tranenfilms, also known as tear film, is a thin, multi-layered fluid that coats the ocular surface between the eyelids and the external environment. It serves as a lubricant for the eyeball, provides a smooth refractive surface for vision, and acts as a barrier to dust and microorganisms. The tear film is traditionally described as comprising three main layers: a lipid (oil) layer produced mainly by the meibomian glands, an aqueous (watery) layer produced by the lacrimal glands, and a mucin layer produced by conjunctival goblet cells and corneal epithelium. These layers work together to protect, nourish, and stabilize the tear film.

The tear film is dynamic and constantly refreshed with every blink. The lipid layer reduces evaporation, the aqueous layer supplies water, electrolytes, and antimicrobial proteins, and the mucin layer helps the tears spread evenly across the ocular surface and adhere to the cornea. Tear film stability is influenced by blinking rate, environmental conditions, eyelid function, and ocular surface health. Disruptions to the tear film can lead to irritation, blurred vision, and fluctuating vision.

Clinically, tear film health is assessed using tests such as tear breakup time (TBUT), Schirmer test for tear production, and osmolarity measurements. Disorders of the tear film include dry eye disease (evaporative or aqueous-deficient), meibomian gland dysfunction, and allergic conjunctivitis. Treatments range from preservative-free artificial tears and lubricants to anti-inflammatory agents, eyelid hygiene, and procedures to reduce tear evaporation or conserve tears, such as punctal plugs.