Ocular surface and precorneal tear film

The ocular surface and precorneal tear film (PTF) constitute a complex functional unit, often termed the Lacrimal Functional Unit (LFU), which is essential for maintaining corneal health and visual clarity (StatPearls, 2023). The PTF is a dynamic fluid layer covering the cornea and conjunctiva, traditionally described as a trilayered structure consisting of an outer lipid layer, a middle aqueous layer, and an inner mucin layer (NIH, 2022). Its primary biological functions include providing a smooth refractive surface for light, lubricating the eyelids during blinking, and protecting the eye from environmental pathogens through antimicrobial proteins (PubMed, PMC7249515). Dysfunction in any component of this system leads to ocular surface diseases, most notably dry eye disease (DED), which is characterized by tear film instability, hyperosmolarity, and inflammation (TFOS DEWS II, 2017). Therapeutic interventions for this system include lubricants to supplement tear volume and anti-inflammatory agents like cyclosporine and lifitegrast that target the underlying immune response (FDA, 2021). Newer treatments such as varenicline nasal spray aim to restore homeostasis by stimulating natural tear production via the trigeminal parasympathetic pathway (PubMed, 34653433).

Other names

Ocular surface systemPrecorneal filmTear filmLacrimal functional unitPTF

Pharmacological agents targeting this system function by supplementing tear volume, reducing T-cell mediated inflammation via calcineurin inhibition, inhibiting leukocyte adhesion through LFA-1 antagonism, or stimulating endogenous tear production via neural pathways.