Ocular surface and tear film layers

The ocular surface and tear film layers represent a complex physiological system comprising the cornea, conjunctiva, and the overlying tear film, which is essential for visual acuity and ocular health (StatPearls, 2023). The tear film is traditionally characterized by three layers: an outer lipid layer from meibomian glands that prevents evaporation, a middle aqueous layer from lacrimal glands containing nutrients and antimicrobial proteins, and an inner mucin layer from goblet cells that ensures wetting of the corneal epithelium (NIH, 2022). This system functions as the eye's primary refractive surface and a critical immunological barrier against pathogens (TFOS DEWS II, 2017). Pathological disruption, often termed Dry Eye Disease (DED), involves a cycle of tear hyperosmolarity and ocular surface inflammation (PubMed, 2021). Pharmacological treatments target this system through various mechanisms, including the use of artificial tears for lubrication, secretagogues like varenicline to increase tear production, and anti-inflammatory agents such as cyclosporine or lifitegrast to inhibit T-cell mediated damage (FDA, 2023). Because this entry describes an entire anatomical system rather than a single protein or receptor, it is classified as a therapeutic area rather than a specific molecular target.

Other names

Precorneal tear filmOcular surface systemTear film unitLacrimal functional unit

Lubrication of the ocular surface, T-cell inhibition via calcineurin inhibition, LFA-1/ICAM-1 antagonism to reduce inflammation, corticosteroid-mediated gene transcription modulation, and nicotinic acetylcholine receptor agonism to stimulate natural tear production.