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The aim of the subcommittee report was to review published evidence describing tear film changes secondary to contact lens wear and to examine the evidence for associations between tear film changes and contact lens–related discomfort (CLD) in order to identify potential etiologies for CLD and strategies for the optimization of comfort. The report comprises two main sections; the first describes biophysical interactions between the contact lens and the tear film, and the second deals with biochemical changes to the tear film associated with contact lens wear. In first considering the tear film structure, recent tomographic, interferometric, and reflectance spectral techniques indicate central corneal tear film thickness values around 3 μm, 1–3 aligning closely with earlier measurements. 4, 5 The thin outermost lipid layer of the tear film, on the order of 50 to 100 nm in thickness, 6, 7 forms the barrier between the environment and the eye. The lipid secretions arise mainly from the meibomian glands through orifices located at the mucocutaneous lid margin junctions, and are combined with a lesser lipid contribution from the eyelid glands of Moll and Zeiss. 8 Spread over the tear film surface by blinking, the lipid layer comprises a thin inner polar layer, overlaid by a thicker outer nonpolar layer. 9, 10 In addition to preventing overspill of tear fluid onto the eyelids and contamination of the tear film by skin lipids, 9, 11 the most significant role of the lipid envelope is considered to be in retarding evaporation from the ocular surface. 12, 13

The aqueous phase of the tear film forms the bulk of the tear film thickness. 8 It arises primarily from the main lacrimal gland …