Tears - biological functions

The tear film serves as the vital interface between the ocular surface epithelium and the external environment. Researchers based in Houston, TX, United States, conducted an extensive literature review covering clinical and basic studies, spanning the 60-year period. Within its composition, the normal tear film is intricately balanced with a specific complement of ions, proteins, and lipids, enabling it to perform its fundamental functions effectively.
One of the primary functions of the tear film is its crucial role as the primary optical surface of the eye. Remarkably, tears and the anterior surface of the cornea contribute to approximately 80% of the eye's refractive power. Beyond its optical significance, the normal tear film acts as a protective barrier for the ocular surface epithelium, shielding it from daily environmental challenges. These challenges encompass various elements like microbes, pollutants, allergens, and environmental conditions such as low humidity, swift air movements from wind or indoor air systems. The lacrimal functional unit (LFU) plays a pivotal role in regulating the production, delivery, and clearance of tears, thereby maintaining a homeostatic environment on the ocular surface. The neural component of the LFU, in conjunction with emotional centers in the brain, communicates with secretory and motor efferent nerves to stimulate tear production and blinking. The tear film, with its intricate structure and composition, plays a multifaceted role in safeguarding the cornea, facilitating wound healing after injury, and ensuring overall eye comfort and high-quality vision. More in the original article.