title: Subretinal electrical stimulation of the rabbit retina with acutely implanted electrode arrays.
abstract: BACKGROUND
  Subretinal implants intend to replace photoreceptor function in patients suffering from degenerative retinal disease by topically applying electrical stimuli from the subretinal space. This study intended to prove the feasibility of a newly developed transchoroidal surgery and, furthermore, of a subretinal electrode array, which closely resembles envisioned human implants to electrically stimulate the visual system in rabbits.
  
  
  METHODS
  Five rabbits (ten eyes) were implanted with a 4x2-electrode array via a transchoroidal access to the subretinal space. The electrodes were connected to an arbitrary stimulus generator to apply voltage pulses. Retinae were accessed by light microscopy after stimulation with various intensities.
  
  
  RESULTS
  The stimulating foil could be introduced into the subretinal space in all eyes. In seven of ten eyes electrically evoked cortical potentials following subretinal electrical stimulation could be elicited. Threshold voltages ranged from less than 0.1 to 2.38 V with a corresponding threshold charge of approximately 1.0 nC per electrode or 10 micro C/cm(2). Histology revealed localized retinal damage over some of the electrodes succeeding stimulation strengths of 2 V and consistent damage over all electrodes succeeding voltages of 3 V.
  
  
  CONCLUSIONS
  The study demonstrates the feasibility of the transchoroidal surgical access to place subretinal implants in rabbit eyes and provides proof of successful cortical activation following subretinal electrical stimulation by an electrode array envisioned for human implantations.
authors.affiliation: University Eye Hospital, Schleichstrasse 12-16, 72076 Tübingen, Germany. gekeler@uni-tuebingen.de
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.forename: Karin
authors.initials: K
authors.lastname: Kobuch
authors.forename: Hartmut Normann
authors.initials: HN
authors.lastname: Schwahn
authors.forename: Alfred
authors.initials: A
authors.lastname: Stett
authors.forename: Kei
authors.initials: K
authors.lastname: Shinoda
authors.forename: Eberhart
authors.initials: E
authors.lastname: Zrenner
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004594:Electrophysiology; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005240:Feasibility Studies; D008839:Microelectrodes; D011817:Rabbits; D012160:Retina / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology