title: Development of very large electrode arrays for epiretinal stimulation (VLARS).
abstract: BACKGROUND
  Retinal implants have been developed to treat blindness causing retinal degenerations such as Retinitis pigmentosa (RP). The retinal stimulators are covering only a small portion of the retina usually in its center. To restore not only central vision but also a useful visual field retinal stimulators need to cover a larger area of the retina. However, large area retinal stimulators are much more difficult to implant into an eye. Some basic questions concerning this challenge should be answered in a series of experiments.
  
  
  METHODS
  Large area retinal stimulators were fabricated as flexible multielectrode arrays (MEAs) using silicon technology with polyimide as the basic material for the substrate. Electrodes were made of gold covered with reactively sputtered iridium oxide. Several prototype designs were considered and implanted into enucleated porcine eyes. The prototype MEAs were also used as recording devices.
  
  
  RESULTS
  Large area retinal stimulator MEAs were fabricated with a diameter of 12 mm covering a visual angle of 37.6° in a normal sighted human eye. The structures were flexible enough to be implanted in a folded state through an insertion nozzle. The implants could be positioned onto the retinal surface and fixated here using a retinal tack. Recording of spontaneous activity of retinal neurons was possible in vitro using these devices.
  
  
  CONCLUSIONS
  Large flexible MEAs covering a wider area of the retina as current devices could be fabricated using silicon technology with polyimide as a base material. Principal surgical techniques were established to insert such large devices into an eye and the devices could also be used for recording of retinal neural activity.
authors: Florian
authors: F
authors: Waschkowski
authors: Stephan
authors: S
authors: Hesse
authors: Anne Christine
authors: AC
authors: Rieck
authors: Tibor
authors: T
authors: Lohmann
authors: Claudia
authors: C
authors: Brockmann
authors: Thomas
authors: T
authors: Laube
authors: Norbert
authors: N
authors: Bornfeld
authors: Gabriele
authors: G
authors: Thumann
authors: Department of Ophthalmology, University Hospital Aachen, RWTH Aachen University, Pauwelsstr 30, 52074 Aachen, Germany. pwalter@ukaachen.de.
authors: Peter
authors: P
authors: Walter
authors: Wilfried
authors: W
authors: Mokwa
authors: Sandra
authors: S
authors: Johnen
authors: Gernot
authors: G
authors: Roessler
mesh_terms: D001698:Biomedical Engineering; D003198:Computer Simulation; D004599:Electric Stimulation Therapy / Q000379:methods; D004567:Electrodes, Implanted; D004867:Equipment Design; D006046:Gold / Q000737:chemistry; D006801:Humans; D007094:Imides / Q000737:chemistry; D007495:Iridium / Q000737:chemistry; D012160:Retina / Q000473:pathology; D012174:Retinitis Pigmentosa / Q000628:therapy*
chemical_list: D007094:Imides; C044458:iridium oxide; D007495:Iridium; D006046:Gold