Corneal blindness is a worldwide health, social, and economic problem that is responsible for up to 5% of blindness in developed countries and 50% in developing countries. It is estimated that at least 10 million people suffer from bilateral corneal blindness, and a larger number suffer from unilateral corneal blindness.
Supported by the European Union and cofinanced by a cooperative multidisciplinary and international research project called CORNEA (see The Cornea Project for more information), our goal is to develop a complication-free, functional, and retainable artificial cornea that restores sight in people with corneal blindness.
The keratoprosthesis Flexicornea1 (I.O. International Ltd., Croydon, UK) is a flexible one-piece disc made of polymetylmethacrylate that is similar to the human cornea. It also contains a series of novel physical, chemical, and polymeric features that should allow (1) firm attachment to the host cornea, (2) prevention of complications commonly associated with keratoprosthesis, (3) provision for a wide-field vision similar to that of a donor cornea, and (4) intraocular pressure measurement and glaucoma detection.
THE FLEXICORNEA IMPLANT
We have implanted the Flexicornea-SD model (Figure 1), with a central visual section diameter of 7 mm and a thickness of 0.3 mm, in 10 rabbits. A thinner skirt section on the implant is 2 mm in diameter, and the thickness in this area remains at 1 mm. An implantation method for use with the Flexicornea has also been designed. This technique is simple, and ophthalmologists with average surgical skills may perform the procedure in approximately 30 minutes.
The objective of our in vivo assessment was to calculate the acceptability and biocompatibility of the shape and size of the Flexicornea in rabbit eyes as a model for humans. We also wished to study the practicality, simplicity, and feasibility of the proposed surgical procedures for the Flexicornea. Therefore, we implanted the Flexicornea-SD in one eye of each rabbit and followed them for 8 weeks. All Flexicornea samples were not coated or chemically treated to improve retention in the eye or prevent serious complications. In vitro and in vivo studies with surface-modified samples are under current investigation. First studies have shown that the surfaces can be modified to adopt to the different requirements such as cell adhesion and proliferation on the skirt and cell repellence on the optical anterior and posterior part.
Results of the study showed that the size and shape were highly suitable and biocompatible with the host eye. In fact, its appearance was similar to the natural cornea (Figures 2 through 5). The size of the Flexicornea (11 mm) and the position of the peripheral edge—near the limbus—caused no adverse reactions, including inflammatory responses. The skirt of the Flexicornea was well tolerated and retained within the host cornea. No adverse reaction or rejection was detected. The holes in the skirt were slowly filled with fibrin, secretions, and most likely cells as well (Figures 4 and 5). No significant increase in intraocular pressure was detected; however, the untreated PMMA did not bind well to the host cornea.
Based on the results, an advanced version of the Flexicornea, the Flexicornea-2 (Figures 6 and 7), was developed. This new model incorporates a series of novel physical and polymer-chemical modifications that will hopefully improve its binding with the host cornea. Furthermore, it should prevent the development of the serious complications responsible for rejection of keratoprosthesis, providing better vision and wider visual field.
Dayshad Darougar, BSc, ARCS(Hons), is the Research and Executive Director of I.O. International Ltd. He states that he is a coinventor of the Flexicornea and not an owner of the invention, is a paid staff member of the I.O.I., and owns shares in the company. He may be reached at +44 7885563629; DDarougar@aol.com.
Sohrab Darougar, MD, DTM&H, FRCS, DSc, is an Emeritus Professor of Public Health Ophthalmology, University of London. He states that he is a coinventor of the Flexicornea and not an owner of the invention, is a research consultant to I.O.I., and owns shares in the company. He may be reached at +44 208 6864711; Darougar@aol.com
Joachim Storsberg, PhD, is the Head of the Research Unit Functional Medical Polymers at the Fraunhofer-Institute for Applied Polymer Research, Potsdam, Germany. He states that he has no financial interest in the companies or products mentioned. He may be reached at +49 331 5681321; joachim.storsberg@iap.fraunhofer.de.
