The ultrastructural basis of corneal dysfunction and the development and optimization of novel therapeutic strategies

The cornea is the transparent window at the front of the eye and is its main focussing element. To fulfil its role it has to be very transparent, very strong and precisely shaped. Transparency, strength and shape are all controlled by the collagen fibrils that make up the cornea, and by the small molecules between them. This happens at different structural levels from the molecular level upwards: collagen molecules form fibrils, which in turn form larger structures called lamellae, which are then stacked up to form the tissue itself. From our previous work and work done by others, we know a lot about why the cornea is transparent and are beginning to understand the arrangement of collagen lamellae that gives rise to the cornea's shape and thus its focusing abilities. However, the precise details are still not known and, until they are, it will not be possible to understand why, in numerous diseases of the cornea, or after different types of surgery on the cornea - including laser surgery - transparency, strength and/or shape are abnormal and vision is lost or very blurred. We will use several new and exciting 3-D biological imaging and powerful X-ray measuring techniques, to explain how collagen fibrils and cells are arranged in the cornea to make it transparent, and how other proteins control this arrangement. We will also explain at a higher structural level how lamellae are arranged to provide form and strength. This will allow us to construct computer models from which to predict changes in corneal shape following given surgical incisions or other treatments to help inform surgeons. We will then explain what goes wrong in several important corneal diseases and investigate methods of preventing or correcting these changes, for example by using stem cell therapy or protein crosslinking. The methods will also allow us to explain why, when the cornea is wounded, tissue strength and transparency are compromised. Again, methods to improve this wound healing such as those mentioned above will be investigated, with the aim of strengthening the cornea whilst preserving transparency. Finally, several research groups in different countries are trying to develop a biological artificial cornea as there is, and is likely to continue to be, a worldwide shortage of donor corneal tissue for graft surgery. Synthetic biology depends on understanding how nature utilises the constituents of a tissue to achieve its vital properties. In the case of the cornea, the knowledge that we will obtain by elucidating the exact relationship between structure and function will be invaluable, and will allow us to collaborate with these groups to drive their constructs more quickly towards a fully functioning artificial cornea.

The cornea of the eye is a uniquely transparent, exquisitely shaped tissue whose functionality depends heavily on the hierarchical ultrastructures and complex microanatomy of its cells and extracellular matrix. Despite the importance of the cornea for vision, the basis of corneal transparency and shape, and their compromise due to injury or disease, are only now starting to be understood in any detail. Our ultimate objective is to build upon the success of our previous studies and relate loss of transparency and changes in corneal shape/astigmatism to tissue micro- and ultra-structure. This will be achieved by taking advantage of recent advances in microfocus synchrotron x-ray scattering, electron tomography, multiphoton laser scanning microscopy and volume scanning electron microscopy to study human foetal corneas, normal and pathological adult corneas, post-surgical corneas and artificial corneal constructs. Our aims are to (i) model corneal transparency at the cellular and fibrillar level, and to extend this to explain the loss of transparency in corneal wounds and diseases; (ii) characterise the full three-dimensional structure of the cornea and explain the structural basis of astigmatism, and demonstrate how surgical treatments can be modeled to predict the cornea's macroscopic behaviour by finite element analysis; (iii) develop and better understand new methodologies for treating or stabilizing corneas, such as cell-based therapies for improving transparency and mechanical strength in corneal wounds and crosslinking methods to stabilize corneas to prevent ectasia; (iv) use the new three-dimensional structural information to assess and improve different approaches being used to develop biological artificial corneal replacements.

The main non-academic beneficiaries will be the patients themselves. Our work on corneal pathologies will aid understanding of the disease mechanisms and drive the development of better treatments from which patients will benefit. Our work on refractive surgery should improve the outcome of these procedures (stronger flap adherence, less likelihood of post-LASIK ectasia or induced astigmatism) and lead to safer treatments, more predictable clinical outcome and better patient satisfaction. We anticipate our work on corneal crosslinking extending the number of keratoconus patients who can undergo the treatment, while our research into microwave therapy may offer new hope to keratoconus who cannot undergo LASIK and whose only current treatment option is corneal transplant.
Other beneficiaries will include our anticipated commercial partners, who would be involved in clinical trials prior to marketing the methods for stabilizing the post-surgical wounds; this would lead to commercial benefit for the company and economic benefit for the UK. Refractive surgery has been carried out on millions of people worldwide, not always without post-operative complications. If we can develop better methods to carry out such surgery, or find methods of improving the outcomes of the current surgery, there will be a huge worldwide benefit to public health. Finally, there is a pressing need for the development of artificial corneal tissue whose properties mimic the natural tissue. Our work to develop a biological artificial cornea will be in collaboration with groups in other countries who are leading the field in this area. If we succeed, it will have a lasting impact on global quality of life, particularly in developing countries where the shortage of donor tissue is already critical.
Timescales are different for different projects within the proposal. For example, our work on methods of epithelial removal prior to corneal crosslinking had an immediate impact on practice, and this should be the case when this work is continued, with the aim of finding a method that does not require epithelial removal. Developing a suitable method to stabilize LASIK flaps, for example by using oral mucosal cells, will take 5 years, including animal trials, and clinical trials would follow. Investigating alternative methods of refractive correction, such as the use of microwaves, may have an impact within a few years, as clinical trials are already underway. Similarly, the corneal constructs created by Professor Griffith are also in early clinical trials, and the optimized constructs arising from our joint research will follow into trials. Finally, developing computer models to predict the outcome of corneal surgeries is a longer-term outcome with widespread potential benefit and may take up to 10 years.