Models for the Human Tear Film
This material is based upon work supported by the National Science Foundation under Grant Nos. 1412085, 1022706 and 0616483,
and by the National Insitutes of Health (NEI) under Grant No. 1R01EY021794.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s)
and do not necessarily reflect the views of the National Science Foundation or the NIH.
Tear Film Group
This was the group
in Summer 2014.
L to r: Rich, Mike, Joe, Longfei, Toby.
Not pictured: Javed Siddique, Ryan Evans.
- U of Delaware Members
- Richard Braun
- Tobin Driscoll
- Michael Stapf, Graduate student for summer 2012 Unidel program and current PhD student on an RA.
- Lan Zhong, Graduate student in AY 2014-15, through the present
- Amy Janett, Graduate student, Summer 2015
- Joe Brosch, Undergraduate student, Spring and Summer 2013, through the present
- Laura Cahill, Undergraduate student, Summer 2015
- Carolyn Begley, Indiana University
- P. Ewen King-Smith, The Ohio State University
- William Henshaw, Rensselaer Polytechnic Institute
- Jeff Banks, Rensselaer Polytechnic Institute
- Kara Maki, Rochester Institute of Technology
- Javed Siddique, Pennsylvania State University at York
- Ranganathan Usha, IIT Madras, India (visited in 07-08 at UD)
- Geoffrey McFadden, NIST
- Daniel Anderson, George Mason University
- Nick Gewecke, UD postdoc, 2011-14, now in a tenure track position at Dalton State in Georgia.
- Graduate students
- Longfei Li, PhD in Applied Math 2014. Longfei accepted the Margaret A. Darrin postdoctoral fellowship at RPI with Bill Henshaw.
- Quan Deng, PhD in Applied Math 2013. Quan joined Amazon in a research position.
- Kara Maki , U of Delaware, PhD in Applied Math 2009. After an IMA Postdoc,
Kara joined the School of Mathematical Sciences at Rochester Institute of Technology
- Alfa Heryudono, U of Delaware, PhD in Applied Math 2008,
now on the faculty in the Department of Mathematics at U Mass Dartmouth.
- Ryan Evans, U of Delaware graduate student, summer 2013 and AY 2013-14.
- Kevin Buckman, U of Delaware graduate student 2013 (Unidel program)
- Jiahua Tang, U of Delaware graduate student 2010 (GEMS support)
- Xiaolin Yang, U of Delaware volunteer summer student 2007, MS in CIS at UD, then to Duquesne U
- Undergraduate students
- Pete Ucciferro, Undergraduate summer student 2007-2009 (NSF REU support, 3 times), Fall 2009 independent study; now at Philadelphia College of Osteopathic Medicine
- Paul Parsons, Undergraduate summer student 2007 (NSF REU support)
- Stacey Watro, Undergraduate summer student 2010 (NSF REU support)
- Douglas Freeman, Undergraduate summer student 2011
- Wai-Kit Ricky Shum, Undergraduate summer student 2011
- R. Christian Paul, Undergraduate summer student 2011
- Kaijing Wang, Undergraduate student summer and fall 2011 (NSF REU support)
- Tianyu Qiu, Graduate student for summer 2012 GEMS program
- Jennifer Bruhns, Undergraduate HHMI scholar (Summer 2011, 2012), Independent study 12S and UG thesis 12-13; starting New England College of Optometry in 2013. Jen won the departmental undergraduate research award in Spring 2013.
- Vikramjit Singh, Undergraduate summer scholar 2012 and UG thesis 12-13.
- Dylan Chapp, Undergraduate summer scholar 2012 and independent study 2012-13. BS in Mathematics 2014. Dylan is currently an RA in the UD CIS department. Dylan won the departmental undergraduate research award in Spring 2014.
- Matthew Moye, Summer 2013 NSF REU student and AY 2013-14. Currently a graduate student in mathematics at NJIT.
- Justin Greer, Summer 2013 NSF REU student. Justin will attend Optometry school in Fall 2015.
This was the group
in Summer 2013.
Back row, l to r: Quan, Joe, Longfei, Dylan, Kevin, Ryan.
Front row, l to r: Toby, Nick, Rich, Matt, Justin.
Not pictured: Christian.
We celebrated a productive summer at lunch that day.
Our group has been collaborating with Carolyn Begley's group at the Indiana University School of Optometry. They use several methods to image the tear film and are willing to share wonderful data with us too. The review article below is our biggest joint effort to date. This collaboration is funded by Carolyn's NIH grant from the National Eye Institute.
Review article on the tear film
A review article on tear films that includes many new results is in press for Progress in Retinal and Eye Research, an invitation only journal, to appear in early 2015. "Dynamics and function of the tear film in relation to the blink cycle" is currently available online at
at the journal's site.
Some articles on tear break up and imaging
- "Tear film dynamics with evaporation, wetting, and time-dependent flux boundary condition on an eye-shaped domain,"
Longfei Li, RJ Braun, KL Maki, WD Henshaw, PE King-Smith,
Physics of Fluids 26, 052101 (2014); doi
- "A Model for Tear Film Thinning With Osmolarity and Fluorescein," RJ Braun, NR Gewecke, CG Begley, PE King-Smith and JI Siddique, Invest. Ophthalmol. Vis. Sci. 55, 1133-1142, 201;
- "Evaporation-driven instability of the precorneal tear film," C-C Peng, C Cerretani, RJ Braun and CJ Radke, Advances in Colloid and Interface Science 206, 250-264, 2014;
- "Tear Film Breakup and Structure Studied by Simultaneous Video Recording of Fluorescence and Tear Film Lipid Layer Images," PE King-Smith, KS Reuter, RJ Braun, JJ Nichols and KK Nichols, Invest. Ophthalmol. Vis. Sci. 54, 4900-09, 2013;
- "Tear Film Images and Breakup Analyzed Using Fluorescent Quenching," PE King-Smith, P. Ramamoorthy, RJ Braun and JJ Nichols, Invest. Ophthalmol. Vis. Sci. 54, 6003-11, 2013;
Some articles on blinking and cooling
The following articles involving blinking appeared recently.
- "Heat transfer and tear film dynamics over multiple blink cycles," Quan Deng, RJ Braun and TA Driscoll, Phys. Fluids 26, 071901 (2014); doi
- "A model for the tear film and ocular surface temperature for partial blinks," Quan Deng, RJ Braun, TA Driscoll and PE King-Smith, Interfacial Phenomena and Heat Transfer 1, 357-381, 2013; doi
- "A model for the human tear film with heating from within the eye," Longfei Li and RJ Braun, Phys. Fluids 24, 062103 (2012); doi
Progress from the Second NSF grant
Review article on the Tear Film
A review article on tear films in the Annual Review of Fluid Mechanics appeared in print
in January 2012. "Dynamics of the Tear Film" is currently available online in
volume 44 of the journal.
A recent talk on our work
- At a BIRS workshop in December 2012, this talk
summarized some of our recent work.
Elements of Thermal Models for the Tear Film
- Longfei Li published a paper on mathematical modeling
for the tear film that captures observed cooling of the ocular surface
during the interblink period. He used models with a thick, thin
or no substrate.
The thick substrate is needed to get cooling of the ocular surface. Longfei
was able to identify optimal thermal properties to match the observed cooling
in eyes. The paper on the subject appeared in Physics of Fluids
(A model for the human tear film with heating from within the eye,
Phys. Fluids 24, 062103 (2012); http://dx.doi.org/10.1063/1.4723870)
Processing of Lipid Microscope Images
- Kaijing Wang(Math major, NSF REU supported) and Christian Paul (Civil engrg major) worked
with Drs Braun and Driscoll to automate classification of images from the lipid microscope
at the Ohio State University's College of Optometry. Three optometrists (Drs King-Smith, Nichols and Nichols)
and their colleagues have made thousands of images of the lipid layer on the front of the eye. Kaijing
and Christian worked on using clustering methods on a relatively small set of images used in a submitted
paper from the Ohio State group. The resutls are very encouraging and work will continue on the project.
This project was supported in part by an REU supplement to our current grant (1022706) and by the HHMI grant
here at UD.
Models for Tear Film and Ocular Surface Interaction
- Jen Bruhns (QBio major, HHMI supported) and Doug Freeman (Math major, NSF REU supported)
worked with Dr Braun on models the connect the tear film and the ocular surface through osmosis
within the cornea. The model connected the tear film with the corneal epithelium that was originally
developed for mouse eyes. Work is ongoing after a great start during the summer.
This project was supported in part by an REU supplement to our current grant (1022706).
Progress from the First NSF grant
Multiple Blink Cycles and the Tear Film
- We are using lubrication theory to develop nonlinear partial
differential equation(s) that govern the free surface of the human tear film
during the complete blink cycle. In the simplest case, the
surface of the film is assumed to be stress free (SF), as if the tear fluid
were pure water; another simplifying limit is that of a very strong insoluble surfactant,
where the film surace stretches uniformly (the uniform stretching limit, or USL).
In either limit, a single pde governs the shape of the free surface; we have extended the work
of Jones et al (Math Med Bio, 2005) by addition additional effects and computing for the whole blink
- We have computed multiple blink cycles for these limiting cases with the simplification
of the sinusoidal motion of the moving lid. In this instance, an MOL method based on uniform finite
differences in space and BDF methods for the resulting ODEs (via DASPK) was used.
While this seems like a radical simplification,
it still gets a number of things right. For example, there is a transition between periodic and
non-periodic tear film evolution for incomplete blinks; that it, the tear film behaves as if there
was a full blink even if the lids d t fully close. Also, after a half-blink, there is a valley
in the tear fluid corresponding to where the lid was; we have quantitative film thickness measurements
from in vivo interference patterns to use for comparison. The sinusoidal lid motion captures the existence of
this valley qualitatively. This work
has appeared in JFM (Braun and King-Smith, JFM 586 (2007) 465-490).
- We have solved the pdes using a modified spectral method and with realistic lid motion
from blinks. The MOL method maps Chebyshev points in space to minimize round off error in the higher
derivatives and uses exact flux values from the boundary conditions when evaluating the ODEs at grid
points; the ODEs are solved using ode15s in Matlab and the code was developed by Alfa Heryudono.
The approximation conserves volume very well, typically
below 0.0001 or better relative error over multiple blink cycles; this is a significant improvement
over the previous method based on the uniform finite difference grid. Using realistic
lid motion, we get better agreement
with the in vivo film thickness measurements from the half blink, and modified results for the transition
from periodic to non-periodic solutions for the film.
This work is accepted for publication in
"Single-Equation models for the Tear Film in a Blink Cycle: Realistic Lid Motion,"
Mathematical Medicine and Biology (Heryudono, Braun, Driscoll, Maki, Cook and King-Smith,
Math Med Biol 24, (2007) 347-377). The presentation Alfa gave at the 2007 APS DFD meeting is available.
- Heryudono and Driscoll have developed radial basis function methods for the these kinds
of problems. They published results for an adaptive rbf method for problems that are second order in space,
which has been published (Driscoll and Heryudono, "Adaptive residual subsampling methods for radial basis
function interpolation and collocation problems," Comp. Appl. Math. 53 (2007) 927). They have also
published the rbf algorithms on www.matlabcentral.com.
Overset Grids in 1D and 2D
- Reflex Tearing in 1D
- An overset grid method has been developed, for a tear film problem incorporating opening and relaxation
while open, as well as more physiological effects, by
Kara Maki. The effects include improved flux boundary conditions for tear supply and reflex tearing,
gravity and evaporation. Kara gave this talk at the APS DFD meeting
in 2007 (and the talk uses this 37 MB movie.
This manscript has appeared in
"An Overset Grid Method for the Study of Reflex Tearing" in Mathematical Medicine and Biology
(K.L. Maki, R.J. Braun, T.A. Driscoll, and P.E. King-Smith, Math Med Biol 25, (2008) 187-214.)
Tear film dynamics in 2D
Kara has also developed
2D models of the post-blink tear film using the Overture framework; Bill Henshaw (LLNL) is helping
considerably with this effort. In the first case, we used lubrication equations for the tear film
and the boundary conditions that specify the film thickness and the pressure at the boundary.
This work is has appeared elctronically in Mathematical
Medicine and Biology (doi:10.1093/imammb/dqp023).
We have also implemented flux boundary conditions;
some preliminary work was presented in this talk at the 2008
APS DFD meeting and elsewhere. (These three movies were used for this talk:
thickness difference (27MB),
thickness difference (50MB),
and thickness difference (28MB).)
The image at left above is the flux direction vectors superimposed over magnitude of the flux;
darker indicates slower flow. Tear fluid is supplied from superior temporal location of the lacrimal
gland, and is extracted at the locations of the puncta which are near the nasal canthus (corner) at the left
end of the domain. The flux conditions are independent of time, which is an
initial model. (In a real blink, the supply and drainage of tear fluid are time dependent and are
closely related to lid motion.) Most of the flow is around the lid margins.
The image at right is the thickness distribution at time 10 when gravity is included
in the simulation. Maroon indicates greater than or equal to 3 microns; the dark blue is the minimum thickness.
The drooping area of maroon indicates a bulge in the meniscus outward from the lid margin.
For the flux boundary conditions we used, the fluid in the upper meniscus
can break through the black line if enough time is allowed between blinks.
This work with flux BCs specified is accepted for publication
in Journal of Fluid Mechanics and will be out in March 2010.
Wetting and evaporation on the cornea in 1D
Dan Anderson and Kat Winter (then a CSUMS undergrad at George Mason) worked with Dr Braun
on a model of the tear film that has a wetting cornea and evaporation from the tear film.
The model was compared with some in vivo observations from King-Smith at Ohio State, and choosing two
parameters to fit the "dry" film thickness and the opening speed of the thin region seemed to give
reasonable agreement between this most basic theory and the experiment. This work has appeared
electronically in Mathematical Medicine and Biology (doi:10.1093/imammb/dqp019).
A talk including some of these results is given in the next section. The talk also
includes some extensions from Pete Ucciferro, an REU student in Summer 09 and an independent
study student in Fall 09; the work was done as part of a GEMS team that included
graduate studente Jiahua Tang, Pam, Chris Raymond and me.
Effect of Corneal Shape
- The effect of the shape of the cornea was studied by R Usha of IIT Madras,
Jeff McFadden of NIST, Ewen King-Smith of OSU as well as Pam, Toby and me.
The substrate is nearly always
assumed to be flat, and Berger's 1973 thesis on the tear film does not explicitly
justify the assumption. The upshot is that we don't
think the substrate has an important effect on tear film dynamics. Along the way,
however, we tried out an Ellis model for the tear fluid and it gave some interesting
results for shock formation on the prolate spheroidal substrate. I gave a
that included these results as well as the competition of a conjoining pressure,
evaporation and gravity at the U of Minnesota in their Chemical
Engineering and Materials Science Department. A paper on this work will appear in the
Journal of Engineering Mathematics.
Capturing Eyelid Motion
Ms. Xiaolin Yang, an MS student in the Department of Computer and Information Sciences,
who worked with Dr Braun on capturing the lid motion during a blink automatically from
high speed digital movies of blinks. The movies were made in the MEC Lab in the UD Department of
Mathematical Sciences with the help of Dr. John Pelesko. She developed a code that could
extract least squares polynomial fits from the
blink movies using Sobel edge detection with some pre- and post-processing. That mathematical approximation
that she generated of a blink has already been incorporated into our efforts to compute the tear film evolution
in two dimensions. She worked with Braun in summer 2006 and January 2007. The code was developed in Matlab,
and the code with some results will appear on this website in the near future.
Mr. Peter Ucciferro (a Quantitative Biology major) and Mr. Paul Parsons (a Physics major)
were supported by an REU supplement for this NSF grant for the
summer of 2007. They worked on evaluating and extending Xiaolin's
algorithms for capturing and mathematically representing eyelid motion during a blink.
Ucciferro and Parsons recorded some observations of blinks and extended the software for
this aspect of the project. One aspect of their work was to use roifill to blur regions around
the eye so that more blink movies could be used. They presented their results in an excellent
joint presentation during the Departmental symposium on summer undergraduate research in August 2007.
- From the APS DFD 2008 virtual press room, LiveScience did an article on
that was presented at the meeting. A seemlingly related article appeared
in SoftPedia at close to the same time.
- Our work was mentioned in a short summary
of highlights from the 2007 meeting of the Tear Film and Ocular Surface Society.
- Many aspects of this project remain open to investigation; join the team! If you're interested,
please contact Dr. Braun.
This was the group
in Summer 2012.
Back row, l to r: Nick, Jen, Vikram, Longfei, Quan and Tianyu.
Front row, l to r: Rich, Toby, Javed, Matt, Dylan and Michael.
We had a mid-summer review that day.
This was the group
in Summer 2011.
Back row, l to r: Longfei, Jen, Ricky and Quan.
Front row, l to r: Javed, Rich, Toby, Doug and Kaijing.
Not pictured: Christian.
We celebrated a productive summer at lunch that day.
This was the group
in Spring 2008.
Back row, l to r: Toby, Rich and Pam.
Front row, l to r: Alfa, Kara and Usha.
Alfa had successfully defended his thesis that day.
View the February 2012 version in Romanian
courtesy of Alexandra Seremina at azoft.
View the January 2015 version in Russian courtesy of Oleg Segal at SciJou.
Last modified 01/21/15 by RJ Braun