What is the anatomy of tear film relevant to dry eye disease (keratoconjunctivitis sicca)?

Updated: Dec 12, 2019
  • Author: C Stephen Foster, MD, FACS, FACR, FAAO, FARVO; Chief Editor: Andrew A Dahl, MD, FACS  more...
  • Print
Answer

The tear film covers the normal ocular surface. It is generally considered to comprise the following 3 intertwined layers (see the image below):

  • A superficial thin lipid layer (0.11 µm) – This layer is produced by the meibomian glands, and its principal function is to retard tear evaporation and to assist in uniform tear spreading [14]
  • A middle thick aqueous layer (7 µm) – This layer is produced by the main lacrimal glands (reflex tearing), as well as by the accessory lacrimal glands of Krause and Wolfring (basic tearing)
  • An innermost hydrophilic mucin layer (0.02-0.05 µm) – This layer is produced by both the conjunctiva goblet cells and the ocular surface epithelium and associates itself with the ocular surface via its loose attachments to the glycocalyx of the microplicae of the epithelium; it is the hydrophilic quality of the mucin that allows the aqueous layer to spread over the corneal epithelium
  • Diagram of three layers of tear film layer. Diagram of three layers of tear film layer.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!