The International Workshop on Meibomian Gland Dysfunction: Report of the Subcommittee on Tear Film Lipids and Lipid–Protein Interactions in Health and Disease

U nderstanding the molecular composition (e.g., proteins and lipids) of the tear film (TF) and the contribution of the meibomian gland to the TF is critical in gaining knowledge about TF instabilities, dry eye syndromes, contact lens (CL) incompatibilities, and other eye diseases. Among its functions, the lipid layer of the TF slows evaporation of the aqueous component, preserves a clear optical surface, and forms a barrier to protect the eye from microbial agents and organic matter, such as dust and pollen. Researchers believe the outer lipid layer is 5 to 10 molecules thick and is composed primarily of wax and sterol esters, possibly intercalated with each other and with proteins rather than forming distinct repeating layers of molecules. 2,3 Evidence from interferometric studies indicate that the TF lipid layer thickness ranges from 20 to 160 nm. The addition of polar and nonpolar layers would add to the lipid thickness, which indicates that the lipid component of the TF may be multiple layers thick or have other contributing sources to correspond with reported thickness measurements. hile the signs and symptoms of TF instability are reasonably well characterized, we are only beginning to understand the specific molecular components of the TF and their relationship with disease and TF stability. The purpose of this review is to examine the meibomian gland's contribu-tion to TF lipids and lipid-protein interactions in health and disease.