gms | German Medical Science

Artificial Vision — The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis

Retina Implant Foundation

19.09.2009, Bonn

The EPIRET Trial

Meeting Abstract

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  • author Peter Walter - Department of Ophthalmology, University Hospital Aachen, RWTH Aachen University, Aachen, Germany
  • author Wilfried Mokwa - Institute for Materials in Electrical Engineering, RWTH Aachen University, Aachen, Germany
  • Uwe Thomas - Giessen, Germany

Artificial Vision – The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis. Bonn, 19.-19.09.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ri20

DOI: 10.3205/09ri20, URN: urn:nbn:de:0183-09ri205

Veröffentlicht: 30. November 2009

© 2009 Walter et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen ( Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.



Between 2003 and 2006 the EPIRET 3 prototype was designed and fabricated. EPIRET 3 is a completely intraocular retinal stimulator with integrated electronics and inductive links for data and energy transfer, data handling, and pulse generation. Twenty five iridium oxide electrodes are mounted on a polyimide base. The implant is hermetically sealed and flexible enough to allow a minimal invasive implantation procedure. Animal experiments demonstrated the long term functionality and biocompatibility of the system. Cortical recordings and metabolic mapping of the visual cortex in cats implanted with the device showed that local activations occurred within the visual cortex corresponding to the area of stimulation in the retina. The system was implanted in six blind volunteers suffering from Retinitis pigmentosa. Lensectomy and vitrectomy were performed using standard techniques. The implant was inserted after enlargement of the corneal incision. The receiver module was inserted in the posterior chamber and transsclerally sutured. The stimulator module was placed on the retinal surface in the macula and retinal tacks were used for stable fixation. The surgery could be perfomed without intraoperative complications. Postoperatively, mild inflammatory responses were seen. The implant was left in place for four weeks. At three time points stimulus thresholds were determined for selected electrodes and perception patterns were recorded in comparison to the stimulation patterns. In all patients the implant could be activated using the inductive link. In all patients the implant was fully functional after the implantation procedure. In all patients phosphenes were elicited. The phosphene patterns corresponded to the stimulus patterns and stimulus thresholds on average were 15 nC/cm². After four weeks the implants were removed and the patients were followed for five months. In one patient a retinal break occurred during the explant procedure. It was treated successfully with laser endocoagulation and silicone oil filling. In three patients tiny epiretinal membranes occurred during the follow-up in the tack areas. None of the volunteers lost their residual visual function. Angiograms showed no vascular changes.

In summary, the EPIRET 3 system proved that a completely implantable retinal implant system without any transscleral connections for data and energy can be fabricated and implanted.

This lecture is available as video recording (Attachment 1 [Attach. 1]).