The tear film is a thin, complex layer of fluid that covers the surface of the cornea and conjunctiva, performing key functions in maintaining the health of the anterior segment of the eye and ensuring optimal quality of vision. Traditionally, a three-layered structure of the tear film has been described, consisting of an outer lipid layer (secreted by the Meibom's glands), a middle aqueous layer (produced mainly by the lacrimal gland and additional lacrimal glands) and an inner mucin layer (produced by the conjunctival cup cells), but modern research indicates a more complex, gradient structure with mucins dispersed throughout the aqueous layer. The normal tear film is approximately 3-10 micrometres thick and undergoes continuous renewal during each blink, which evenly distributes tears across the surface of the eye.<\/p>\n\n\n\n
The tear film performs a number of important physiological functions, including moisturising and nourishing the aneurysmal cornea, supplying oxygen to its epithelium, mechanical cleansing of microorganisms and debris, immune defence through the immunoglobulins and lysozyme contained in tears, and optical smoothing of the corneal surface for visual acuity. Disturbances in tear film stability and composition lead to dry eye disease<\/a> (dry eye disease), manifested by symptoms such as burning sensation, foreign body sensation, congestion, paradoxical tearing and variable deterioration of visual acuity. Tear film assessment includes tests such as the Schirmer test, tear film break-up time (TBUT), evaluation of tear meniscus height and advanced imaging methods such as lipid layer interferometry and meibography.<\/p>","protected":false},"featured_media":0,"parent":0,"template":"","meta":{"_acf_changed":false},"class_list":["post-4728","slownik","type-slownik","status-publish","hentry"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t