Ocular tear film and ocular surface

The ocular tear film and ocular surface constitute a complex functional unit essential for maintaining visual clarity and ocular health (StatPearls, 2023). The tear film is a dynamic, multi-layered structure—comprising lipids, aqueous components, and mucins—that provides a smooth refractive surface, lubricates the eyelids, and serves as a protective barrier against environmental pathogens (TFOS DEWS II, 2017). This system is maintained by the lacrimal functional unit, which includes the lacrimal glands, corneal and conjunctival epithelium, and meibomian glands. Dysfunction in any of these components, often driven by inflammation or desiccation, leads to dry eye disease and potential ocular surface damage (NIH, 2022). Therapeutic interventions target this system through various mechanisms, including the use of immunomodulators to suppress inflammation, secretagogues to enhance tear production, and lubricants or lipid-stabilizers to restore tear film homeostasis (FDA, 2023).

Other names

Precorneal tear filmOcular surface unitLacrimal functional unitLFUTear film

Drugs targeting the ocular tear film and ocular surface primarily act through immunomodulation, such as inhibiting T-cell activation and cytokine release (e.g., Cyclosporine), or by antagonizing the LFA-1/ICAM-1 interaction to reduce leukocyte infiltration (e.g., Lifitegrast) (StatPearls, 2023). Other mechanisms include the stimulation of the trigeminal parasympathetic pathway to increase natural tear production (e.g., Varenicline) and the application of semifluorinated alkanes to stabilize the lipid layer and prevent evaporation (e.g., Perfluorohexyloctane) (FDA, 2023).