Polymer-based Artificial Cornea
Damage to the eye’s cornea restricts vision. As part of the EU’s "Artificial Cornea" project, a polymer-based corneal prosthesis that satisfies a number of complex requirements has now been developed.
The term "cornea" is used to designate the crystal-clear, curved front part of the eye that is wetted by tears. It contributes to refraction of light and represents the external closure of the eye. Damage to the cornea, for instance, as the result of an accident or illness, limits vision. A corneal transplant is one approach to remedying such a situation – but not enough corneas are available from donors to meet patient needs.
Now, a polymeric material and manufacturing method for a prosthetic cornea have been developed at the Fraunhofer Institute for Applied Polymer Research (IAP) in Potsdam-Golm. The tiny artificial cornea must satisfy a variety of complex requirements. On the one hand, the cells of the surrounding tissue must bond firmly to the outer edge of the implant. At the same time, no cells should adhere to the center of the artificial cornea, as vision would otherwise be impaired. Furthermore, the outer surface of the artificial cornea must be wettable by tears; otherwise, it would not be possible to see through the front of the implant. Wetting by tears is also why the eyelid can slide over the implant without friction.
The material employed for the artificial cornea is a water-repellant polymer that already finds use in ophthalmology in intraocular lenses. To achieve the desired properties, the outer edge of the implant is first coated with several special polymers. Finally, a special protein is applied that allows the surrounding natural cells to bond and grow. The result: the cells of the surrounding tissue attach themselves to the implant, providing the artificial cornea with additional stability.
This ophthalmologic prosthesis was created through a joint effort involving the medical community and manufacturers in the EU’s "Artificial Cornea" project. Initially, the artificial corneas were tested in prepared eyes from pigs and special cell cultures. Following this, more refined models were tested on rabbits. Over time, the optics were reduced in size and the outer edge of the implant increased in size in order to have a more stable construct. In 2009, the first prosthesis was implanted successfully; additional implantations are planned for 2010.
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