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M. Brelen, P. De Potter, M. Gersdorff, G. Cosnard, C. Veraart, J. Delbeke; A Minimally Invasive Technique for the Implantation of a Spiral Cuff Electrode Around the Intra–orbital Section of the Optic Nerve . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1487.
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Purpose: Research into visual prosthetics is expected to enhance the management of blind patients with incurable outer retinal degenerative diseases. Substantial evidence shows that useful visual sensations can be produced by controlled electrical stimulation of the optic nerve. In order to make the optic nerve visual prosthesis (ONVP) more acceptable, safer and less invasive implantation techniques have been developed. Methods: This study complies with the declaration of Helsinki and the protocol has been approved by the ethical committee of the School of Medicine at St–Luc University Hospital. Written informed consent was obtained where required. A medial transconjunctival approach was used to implant the stimulating electrode around the intra–orbital section of the optic nerve. Previously, an electrode was implanted on the intracranial part of the optic nerve which required more invasive surgery. The new technique allows sufficient exposure of the nerve after disinserting only one rectus muscle and performing a lateral canthotomy. The procedure was initially tested in chronic animal implantations (rabbits) and then acutely in eight human cadavers and in five patients undergoing eye enucleation. Finally, a 68 year old blind patient suffering from retinitis pigmentosa was chronically implanted in May 2004. During the same procedure the other components of the ONVP (neurostimulator and telemetric antenna) were also implanted. Results: There were no post–operative complications following any of the surgical procedures. The human volunteer who is chronically implanted with the ONVP had no fundoscopic changes, the fluoroangiogram was normal and eye movements recovered fully a few weeks after the operation. A post–operative 3D reconstruction CT was taken which shows the position of all the implanted components. Stimulation of the optic nerve in this patient elicits visual sensation and cortical visual electrically evoked potentials can be recorded. Conclusions: Intra–orbital implantation of the spiral cuff electrode is faster and safer than implanting the cuff intra–cranially. Preliminary assessments suggest that this type of ONVP could work as well as a device which stimulates the optic nerve intra–cranially.
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