Preocular tear film mucous layer

The preocular tear film mucous layer is a complex physiological structure that serves as the innermost component of the tear film, situated directly atop the corneal and conjunctival epithelial surfaces [3, 9, 11]. It is primarily composed of high-molecular-weight glycoproteins known as mucins, which are categorized into membrane-associated mucins (e.g., MUC1, MUC4, and MUC16) that form the glycocalyx and secreted mucins (e.g., MUC5AC) primarily produced by conjunctival goblet cells [2, 8, 14]. This layer is essential for reducing the surface tension of the aqueous tear fluid, ensuring boundary lubrication during blinking, and providing a physical and chemical barrier against pathogens and environmental particulates [11, 16, 17]. Dysfunction of the mucous layer—characterized by reduced mucin production or goblet cell loss—is a hallmark of ocular surface diseases, including dry eye disease and Sjögren's syndrome [6, 10, 16]. Pharmacological management typically involves the use of mucin secretagogues such as diquafosol and rebamipide, which enhance mucin secretion and goblet cell health, as well as the application of artificial lubricants and anti-inflammatory agents to stabilize the tear film and protect the ocular surface [2, 4, 12].

Other names

Ocular surface mucous layerTear film mucin layerOcular mucous layerTear film mucous layerMucous layer of the preocular tear film

Drugs targeting the preocular tear film mucous layer function by stimulating the production and secretion of mucins from goblet and epithelial cells, or by providing exogenous lubrication and hydration. Secretagogues such as diquafosol act on P2Y2 receptors to trigger mucin release, while rebamipide increases goblet cell density and upregulates the expression of membrane-associated mucins. Anti-inflammatory agents further support the layer by preventing the apoptosis of mucin-secreting cells.