The Tear Film: Anatomy and Physiology

This chapter explores the normal structure and function of the tear film. Normal properties and composition of tears as well as the structure of the aqueous, mucin, and meibomian layers are discussed. The role of supporting structures such as the eyelids, meibomian glands, and goblet cells in the lacrimal functional unit (LFU) is also reviewed. Finally, the physiologic roles of the tear film, including lubrication and nutrition of the ocular surface, visual function, anti-inflammatory and healing properties, and its role in ocular surface nerve modulation are all examined.