MRes Bioengineering Research Project
Title of the project: Fluid mechanics in the eye
Supervisor 1: Dr Jennifer Siggers
Department: Bioengineering
Imperial College campus: South Kensington
email: j.siggers@imperial.ac.uk
Project Description:
Ocular fluid mechanics governs many physiological processes that are crucial to sight. There are
many problems in this area that are worth studying. A few are highlighted in this project outline, but
students are welcome to investigate other related aspects.
1. Retinal detachment is a serious condition that can lead to sight loss if not treated immediately. It
affects about 1 in 300 people during their lifetime, with two thirds of cases occurring in myopic
subjects. A survey in the USA in 2007 revealed that severe sight loss is rated amongst adults in the
USA as the most feared health condition (more than paralysis, HIV/AIDS, cancer, stroke and heart
attack/heart disease). Most retinal detachments occur as a result of a tear or a hole forming in the
retina itself. Vitreous humour can then pass through the hole, and the retina comes away from
choroid, which contains vessels that would normally supply its blood. Holes can form due to
degeneration of the retina itself, whilst tears form as the vitreous humour degenerates, pulling apart
the retina. However, many retinal breaks do not lead to retinal detachment. If it were possible to tell
which tears/holes are at most risk of leading to subsequent detachment, the information could be
used to provide preventative treatment to prevent subsequent detachment.
The vitreous humour is a non-Newtonian fluid with a complicated rheology. During the normal aging
process the vitreous humour degenerates, losing its elasticity and becoming a purely viscous fluid. If
this process happens irregularly then patches of highly elastic vitreous humour could remain strongly
attached to the retina. During rotations of the eye, the vitreous humour flows within the vitreous
cavity. Coupled with this motion, the highly elastic fluid could exert strong forces that pull the retina
away from the wall. In this project you will develop a mathematical model of the fluid flow to
understand the forces exerted on the retina by a flowing fluid. Starting with a viscous fluid, we will
build on the model to consider also the effect of viscoelasticity and degradation of the vitreous
humour, as well as including the effects of treatment such as pneumatic retinopexy.
2. Closed-angle glaucoma causes severe loss of sight through optic neuropathy. It is less common
than open-angle glaucoma, but tends to appear very quickly and causes much pain to the sufferer. It
is thought to be caused by the iris buckling forward within the eye (anteriorly) and making the angle
of the eye smaller. In turn that means the aqueous humour cannot easily flow out of the eye, and
the intra-ocular pressure rises sharply, leading to the death of the retinal ganglion cells. The reason
for the buckling of the iris is thought to be that the pressure behind it is too large, forcing it forward.
In this project, you will investigate some of the risk factors for this condition using a mathematical
and numerical model.
3. Central retinal vein occlusion is a serious condition in which the main vein in the optic nerve
becomes occluded at the back of the eye, blocking the outflow of blood, which means that blood
pressures rise within the eye, leading to damage to the retina and possible blindness due to
ischaemia.
Key techniques: (please include only the names of techniques, not a description)
Fluid dynamics
Non-Newtonian rheology
Mathematical modelling
References:
This review is for background reading in the fluid mechanics of the eye:
Siggers JH, Ethier CR. Fluid mechanics of the eye. Annual Reviews of Fluid Mechanics Vol. 44, pages
347--372 (2012). DOI: 10.1146/annurev-fluid-120710-101058
The following papers give more detailed treatment, showing the types of research that have been
done on these problems (numbered according to the problem):
Problem 1. Meskauskas J, Repetto R, Siggers JH. Oscillatory motion of a viscoelastic fluid within a
spherical cavity. Journal of Fluid Mechanics Vol. 685, pages 1—22 (2011) doi:10.1017/jfm.2011.263
Problem 1. Meskauskas J, Repetto R, Siggers JH. Shape change of the vitreous chamber influences
retinal detachment and reattachment processes: is mechanical stress during eye rotations a factor?
Investigative Ophthalmology and Visual Science, Vol. 53(10), pages 6271--6281 (2012) DOI:
10.1167/iovs.11-9390
Problem 2. Huang EA, Barocas VH. Active iris mechanics and pupillary block: Steady-state analysis
and comparison of risk factors. Annals of Biomedical Engineering Vol. 32, Issue 9, pages 1276—1285
(2004)
Problem 3. A ‘‘throttle’’ mechanism in the central retinal vein in the region of the lamina cribrosa.
Williamson TH. British Journal of Ophthalmology Vol. 91, pages 1190–1193 (2007). doi:
10.1136/bjo.2006.102798