Universities are full of networks and if you start a collaboration with one person, they will talk about it to their friends and before you know it people will come knocking on your door and ask for experiments to be done. I have had a couple of meetings with colleagues in Eye and Vision Sciences the University of Manchester who are working on the condition Keratonoconus. This is where the cornea thins and can bulge out distorting vision. The symptoms are an engineering problem, if the cornea thins it will suffer a dramatic reduction in its bending stiffness (which scales as the third power of the thickness) and thus a 20% thinning leads to a 50% loss in bending stiffness. if you can’t get a cornea transplant you have to use solutions such as a rigid contact lenses, transparent implants, or most scarily chemically cross-linking the collagen in the cornea to make it a more rigid material.

This is now a fairly standard clinical opthalmic procedure, where riboflavin is the cross-linker and UV radiation initiates the reaction. But, it appears that no-one really knows how much the stiffness is changed, nor have they thought about the mechanics in great detail. That may be OK as long as the patients outcome is improved but it worries me as a scientist. Colleagues in Eye and Vision sciences had heard that we have a nanoindenter, and that we were already looking at the mechanical properties of soft contact lenses in another collaborative project. Hence our meeting today to see if we can help. It appears that a fraction of donated corneas are not suitable for transplantation and can be used (subject to ethical approval of course) to study their mechanical properties. What is of interest to me is a better understanding of how the mechanical properties of the cornea change with this cross-linking treatment. Because of the dominant influence of thickness, you need a much larger change in corneal elastic modulus to compensate for the thinning and I am surprised that this crude cross-linking approach achieves the mechanical compensation without causing other effects. this will be a challenging project because of the small sample size (the cornea is < 100 microns in thickness and I would like to study the spatial variation in mechanical properties to see if the riboflavin has diffused throughout the cornea to promote cross-linking.

The scary thing with all this is that, despite not being fully understood, the treatment is carried out routinely.