Working Toward Artificial Corneas

Keratoconus is a degenerative disorder of the eye affecting around one person in every thousand. Patients with this disease experience distorted vision due to a misshaping and uneven surface of their cornea, the main refracting lens in the eye made up of the protein collagen. Vision can be corrected by rigid contact lenses or in more severe cases, surgery.

Prof. Keith Meek, Head of the Structural Biophysics Research Group at Cardiff University, has been using X-ray scattering techniques, first at Daresbury's Synchrotron Radiation Source (SRS) and now at its successor Diamond Light Source in Oxfordshire, to perform structural analysis of the cornea. By shining specially tuned X-rays onto corneal samples, Prof. Meek's group has been able to map the orientation and thickness of collagen in corneas both with and without keratoconus.

They found that the cornea has a highly specific fibrous collagen arrangement that is lost in keratoconus. These changes are believed to be pivotal in the progression of the disease and to the development of the keratoconus cornea's characteristic cone shape. Since the cornea is usually a precise curve, light reaching a keratoconus cornea is not refracted properly and therefore the patient's vision is drastically affected.

Effective surgery is available to correct this problem but it is not without its complications. Prof. Meek explains, "The significance of this research is that with a greater understanding of the structure of the cornea at the molecular level, we are able to suggest methods for improving corneal surgery by increasing our understanding of how physical disruption of the cornea's structure can lead to refractive changes."

He adds, "Another aspect to the research is that, due to the fact that in many parts of the world the demand for donor corneas far outstrips the supply, the need to develop an artificial cornea has increased.

In theory it would take months to scan a single cornea using a conventional laboratory source, but due to the high intensity of Diamond's X-rays, a cornea can be scanned in just a few hours. In addition, because synchrotron X-rays can be focussed to a tiny spot, we can generate more detailed maps of corneal structure than ever before. In 12 months time at Diamond, the achievable spot size on the non-crystalline diffraction beamline will be in the order of 10 microns, which is less than a 10th the size of a human hair.

This means that, within a few years, the work will be at a stage where it can feed into the development of artificial biological corneal constructs that mimic the remarkable natural properties of this extraordinary tissue"

With around 65,000 penetrating corneal graft procedures being carried out worldwide each year², this research is playing an important part in advancing eye surgery techniques that are vital to improving the quality of life of those affected by serious eye diseases and disorders.

¹Laser-assisted in situ keratomileusis

²Source: Eye Journal Dec 2008