Ocular surface tear film and mucus layer (OSTF)

The ocular surface tear film and mucus layer is a complex, multi-layered fluid structure essential for maintaining the health and optical clarity of the eye (Dartt & Willcox, 2013, Exp Eye Res). Traditionally described as a trilayer consisting of an outer lipid layer, a middle aqueous layer, and an inner mucin layer, modern models view it as an integrated mucoaqueous gel protected by a surface lipid film (TFOS DEWS II, 2017, Ocul Surf). Its primary biological functions include providing a smooth refractive surface for vision, lubricating the eyelids during blinking, and protecting the cornea from environmental pathogens through antimicrobial proteins like lysozyme and lactoferrin (Willcox et al., 2017, Ocul Surf). In pathological states such as dry eye disease (DED), the stability of this film is compromised, leading to hyperosmolarity and inflammation (Craig et al., 2017, Ocul Surf). Therapeutic interventions target this system through various mechanisms, including the use of artificial tears for volume replacement, secretagogues like Diquafosol to enhance mucin production, and anti-inflammatory agents like Cyclosporine to restore homeostatic balance (Jones et al., 2017, Ocul Surf). Recent advancements also focus on stabilizing the lipid layer using Perfluorohexyloctane to prevent evaporative tear loss, highlighting the film's role as a dynamic physiological target (Bausch + Lomb, 2023).

Other names

Precorneal tear filmTear filmOcular surface filmLacrimal filmMucoaqueous layer

Drugs targeting this system act by supplementing tear volume (lubricants), stabilizing the lipid layer to prevent evaporation (perfluorohexyloctane), stimulating the secretion of mucins and aqueous components (diquafosol, varenicline), or reducing the inflammatory cycle that destabilizes the film (cyclosporine, lifitegrast) (TFOS DEWS II, 2017, Ocul Surf).