Ocular surface (Tear film and corneal epithelium) (OS)

The ocular surface tear film and corneal epithelium constitute a complex functional unit essential for maintaining visual clarity and ocular health. The tear film is a trilayered structure consisting of an outer lipid layer produced by meibomian glands, a middle aqueous layer from lacrimal glands, and an inner mucin layer secreted by goblet cells and the corneal epithelium. This system provides a smooth refractive surface, lubricates the eyelids, and serves as a primary defense barrier against pathogens and environmental insults. Dysfunction in any component of this system leads to ocular surface diseases, most notably dry eye disease, characterized by inflammation, hyperosmolarity, and epithelial damage. Therapeutic interventions range from palliative lubricants to immunomodulators that target the underlying inflammatory cycle to restore the homeostatic balance of the ocular surface environment.

Other names

Ocular surface systemPrecorneal tear filmCorneal epithelial barrierOcular surface unit

Drugs targeting this system typically act by modulating inflammatory pathways (e.g., T-cell inhibition via Cyclosporine), blocking integrin-mediated lymphocyte adhesion (Lifitegrast), stimulating natural tear production via nicotinic acetylcholine receptors (Varenicline), or providing physical lubrication and osmoprotection (artificial tears).