Tear film and corneal epithelial surface

The tear film and corneal epithelial surface represent a complex physiological system essential for maintaining ocular health and visual clarity. The tear film is composed of three primary layers—lipid, aqueous, and mucin—which work in concert to provide a smooth refractive surface, lubricate the eyelids, and protect the underlying corneal epithelium from environmental damage and pathogens [1][2]. The corneal epithelium itself serves as a tight-junction barrier that regulates the transport of ions and water while preventing the entry of microbes into the corneal stroma [1]. Dysfunction within this system, often referred to as dry eye disease or ocular surface disease, involves a cycle of tear film instability, hyperosmolarity, and inflammation [2][3]. Therapeutic strategies targeting this system include the use of lubricants to supplement tear volume, immunomodulators like cyclosporine to reduce inflammation, and lipid-based agents to prevent evaporation [4][5]. Maintaining the integrity of this interface is critical, as chronic disruption can lead to corneal scarring, ulceration, and significant visual impairment [3][6].

Other names

Ocular surfacePrecorneal tear filmTear film-corneal interface

Drugs targeting this system act through various mechanisms: immunomodulators like cyclosporine inhibit T-cell activation to reduce inflammation [4]; LFA-1 antagonists like lifitegrast block the interaction between ICAM-1 and LFA-1 to decrease cytokine release [5]; lubricants and osmoprotectants provide physical moisture and stabilize tear osmolarity [1]; and lipid-based agents prevent evaporative tear loss [2].