Walter P.

Universität zu Köln, Zentrum für Augenheilkunde, Klinik und Poliklinik für Netzhaut- und Glaskörperchirurgie, Köln

Introduction: Due to new developments in fabrication and microelectronics and also after considerable improvements have been obtained in microsurgery of the eye it became possible to integrate microelectronic devices into opththalmological implants. The implants were encapsulated by biocompatible materials. At present, implants are under development for electrical retinal stimulation (Retina Implants), for telemetric determination of the intraocular pressure and for projection of visual information onto the retinal surface.
Methods: Implants are fabricated using micromachining techniques and flexible substrates. Encapsulation is achieved by silicone polymers. Biocompatibility tests are performed with direct and indirect contact experiments in-vitro and in-vivo. The functionality of the prototype systems are evaluated in animal experiments.
Results: For electrical retinal stimulation Retina Implant prototypes are investigated. It has been shown that the implantation and fixation even of complex implant structures is possible. It has further been shown that electrical stimulation yielded cortical responses. Recently, the topographic response of the visual cortex after retinal stimulation has been demonstrated in the cat. Implantable tonometers using pressure sensors integrated into intraocular lenses have been developed and are now under investigation to prove their biocompatibility and long term stability. Implantation is comparable with a standard cataract procedure and the inthe- bag-implantation can be done by folding the new lens and inserting it through a 5.5 mm incision. The fabrication of intraocular picture projectors as an intraocular visual aid is under development. These devices are planned for irreversible anterior opacifications as in trachoma or after severe trauma when there is no perspective of a keratoplasty or a keratoprosthesis.
Discussion: Interdisciplinary cooperation between ophthalmologists and engineers and the availability of high-tech resources made it possible to fabricate new active devices for implantation in the eye for diagnostic or therapeutic approaches. With the development of these implants new perspectives for otherwise untreatable situations occur, e.g. for Retinitis pigmentosa or severe explosion trauma and others. Supported by BMBF, DFG, MWF of the state of NRW and Köln Fortune.

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