Synthetic cornea solves problem of transplant rejection
24 May 2010
An artificial cornea made from specially adapted lens polymer
is bringing sight to many patients who can't tolerate donor corneas.
40,000 people in Europe who become blind after an accident or
illness join the queue for a new cornea. For many patients, a
corneal transplantation could restore the ability to see, however,
some of these cannot tolerate donor corneas.
Dr Joachim Storsberg of the Fraunhofer Institute for Applied
Polymer Research IAP in Potsdam-Golm developed the material and
production process for a corneal prosthesis made of plastic. These
can help patients who are unable to tolerate donor corneas due to
the special circumstances of their disease, or whose donor corneas
were likewise destroyed. In recognition of this accomplishment, Dr Storsberg is being awarded the 2010 Joseph von Fraunhofer Prize.
|Dr Joachim Storsberg holding a synthetic corneal implant. (Photo
credit: Fraunhofer/ Dirk Mahler)
The miniscale artificial cornea has to meet almost contradictory
specifications: on the one hand, the material should grow firmly
together with the cells of the surrounding tissue; on the other
hand, no cells should settle in the optical region of the artificial
cornea ie the middle — since this would again severely impair the
ability to see. Also, the outer side of the implant must be able to
be moistened with tear fluids, otherwise the implant will cloud up
on the anterior side.
Encountering these problems would require the patient to get a new
lens prosthesis after
a relatively brief period of time. In addition, the outer side of the
implant must be able to be moistened with tear fluid, so that the
eyelid can slide across it without friction.
Dr Storsberg found the
solution with a hydrophobic polymer material. This material has been
in use for a long time in ophthalmology, such as for intraocular
lenses. In order for it to satisfy the various characteristics
required, complex development steps were necessary. The material was
thoroughly modified on a polymer-chemical basis, and subsequently
re-tested for public approval.
In order to achieve the desired characteristics, the edge of the
implant was first coated with various, special polymers. Then, a
special protein was added that contains the specific sequence of a
growth factor. The surrounding natural cells detect this growth
factor, are stimulated to propagate and populate the surface of the
corneal margin. Thus, the cells of the surrounding tissue grow with
the implant, and the artificial cornea attains stability.
The eye prosthesis was developed jointly with physicians and manufacturers
over three years in the EU project Artificial Cornea. In a first
step, they sent the chemical-biomimetic coated implant to Dr Karin Kobuch of the Poliklinik für Augenheilkunde at the Regensburg
University Medical Center and to the medical center at the Technical
University of Munich. The physician examined the artificial corneas
in dissected pigs eyes and specialized cell cultures.
Eventually, the team under Dr Gernot Duncker and Dr Saadettin Sel of
the University Center for Ophthalmology in Halle (Saale) tested the
more complex models in rabbits. There, the design was further
refined: the optics were made smaller, and the implant haptic
enlarged in order to maintain a more stable construction. Miro GmbH
manufactured the implant, robin GmbH handled the distribution and
sales and supported the specially adapted implantation centres in
Europe. By 2009, a prosthesis was already successfully in use;
further implantations are anticipated during the first six months of