The influence of non-polar lipids on tear film dynamics

M. Bruna, C. J. W. Breward

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


© 2014 Cambridge University Press. In this paper we examine the effect that physiological non-polar lipids, residing on the surface of an aqueous tear film, have on the film evolution. In our model we track the evolution of the thickness of the non-polar lipid layer, the thickness of the aqueous layer and the concentration of polar lipids which reside at the interface between the two. We also utilise a force balance in the non-polar lipid layer in order to determine its velocity. We show how to obtain previous models in the literature from our model by making particular choices of the parameters. We see the formation of boundary layers in some of these submodels, across which the concentration of polar lipid and the non-polar lipid velocity and film thickness vary. We solve our model numerically for physically realistic parameter values, and we find that the evolution of the aqueous layer and the polar lipid layer are similar to that described by previous authors. However, there are interesting dynamics for the non-polar lipid layer. The effects of altering the key parameters are highlighted and discussed. In particular, we see that the Marangoni number plays a key role in determining how far over the eye the non-polar lipid spreads.
Original languageEnglish (US)
Pages (from-to)565-605
Number of pages41
JournalJournal of Fluid Mechanics
StatePublished - Apr 4 2014
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-013-04
Acknowledgements: The authors acknowledge many very useful discussions with the OCCAM 'Eye Team': R. J. Braun, A. J. Bron, E. A. Gaffney, C. P. Please, J. M. Tiffany and V. S. Zubkov. We especially thank J. A. Carrillo, C. Ortner and T. P. Witelski for helpful discussions on the numerical aspects of this work. This publication is based on work supported by award number KUK-C1-013-04 made by King Abdullah University of Science and Technology (KAUST). M.B. is grateful to St John's College, Oxford for funding in the form of a Junior Research Fellowship.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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