Wireless retina implant with large visual field

We present the concept of a novel epiretinal prosthesis, consisting of a foil-based, miniaturized electronics with wireless optical energy and signal transmission and integrated electrostimulation. The aim is achieving a wideangle projection to create a large visual field. The implant having a diameter of 14 mm consists of a mosaic-like array of thinned silicon-based photodiodes combined with a polyimide foil. This thin implant, realized on a flexible foil for the first time, adapts to the curvature of the eye. Thin-film stimulation electrodes on the foil are electrically connected to the photodiodes. The influence of the electrode geometry on the electrical current density at the location of electrostimulation is investigated by computer simulations. First experiments towards realization of via holes in a 10 μm thick polyimide layer were successful and led to vias with inclined sidewalls and rounded openings. This shape is advantageous concerning uninterrupted conductor paths leading from the photodiodes to the stimulation electrodes.

Extraocular Surgical Approach for Placement of Subretinal Implants in Blind Patients: Lessons from Cochlear-Implants

In hereditary retinal diseases photoreceptors progressively degenerate, often causing blindness without therapy being available. Newly developed subretinal implants can substitute functions of photoreceptors. Retina implant extraocular surgical technique relies strongly on cochlear-implant know-how. However, a completely new surgical approach providing safe handling of the photosensor array had to be developed. The Retina Implant Alpha IMS consisting of a subretinal microphotodiode array and cable linked to a cochlear-implant-like ceramic housing was introduced via a retroauricular incision through a subperiosteal tunnel above the zygoma into the orbit using a specially designed trocar. Implant housing was fixed in a bony bed within a tight subperiosteal pocket in all patients. Primary outcomes were patient short term safety as well as effectiveness. Nine patients participated in the first part of the multicenter trial and received the subretinal visual implant in one eye. In all cases microphotodiode array pull-through procedure and stable positioning were possible without affecting the device function. No intraoperative complications were encountered. The minimally invasive suprazygomatic tunneling technique for the sensor unit as well as a subperiosteal pocket fixation of the implant housing provides a safe extraocular implantation approach of a subretinal device with a transcutaneous extracorporeal power supply.