title: Functional outcome in subretinal electronic implants depends on foveal eccentricity.
abstract: OBJECTIVE
  An active microelectronic subretinal implant, developed to replace the photoreceptive function in hereditary degenerations of the outer retina, has been applied in a pilot and clinical study in patients with end-stage retinal degeneration.
  
  
  METHODS
  The study population comprised 20 blind patients, all of whom lost vision as result of a hereditary retinal disease. An active visual implant was placed surgically within the subretinal space of each patient: subfoveal placement in eight patients (group 1) and parafoveal placement in 12 (group 2). Standardized low-vision tests, including light perception, light localization, movement detection, grating acuity, and visual acuity by Landolt C-rings, were used under masked, randomized implant-OFF and implant-ON conditions. For the chip-mediated vision functional results of both subject groups were compared.
  
  
  RESULTS
  Three of 20 patients were excluded from analysis because of surgical or technical implant issues. Among patients with nonfoveal placement of the implant, 80% could perceive light, 10% recognized location, and 10% correctly distinguished stripe patterns up to a resolution of 0.33 cycles/degree. No nonfoveal placement patient passed the motion or Landolt C-ring tests. When the implant was placed subfoveally, 100% of patients could perceive light and determine light localization, 75% could resolve motion up to 35°/s, 88% correctly distinguished stripe patterns up to a resolution of 3.3 cycles/degree, and 38% passed a Landolt C-ring test with a decimal visual acuity of up to 20/546 (logMAR 1.43).
  
  
  CONCLUSIONS
  Subfoveal placement of active subretinal visual implants allows superior measurable outcomes compared to para- or nonfoveal placement locations. (ClinicalTrials.gov numbers, NCT01024803, NCT00515814.).
authors.affiliation: Center for Ophthalmology, University of Tübingen, Tübingen, Germany.
authors.forename: Katarina
authors.initials: K
authors.lastname: Stingl
authors.forename: Karl-Ulrich
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.forename: Akos
authors.initials: A
authors.lastname: Kusnyerik
authors.forename: Helmut
authors.initials: H
authors.lastname: Sachs
authors.forename: Eberhart
authors.initials: E
authors.lastname: Zrenner
mesh_terms: D001766:Blindness / Q000534:rehabilitation; D004567:Electrodes, Implanted; D005260:Female; D005584:Fovea Centralis / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology; D010865:Pilot Projects; D012162:Retinal Degeneration / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome; D014787:Vision Tests; D014792:Visual Acuity / Q000502:physiology; D014796:Visual Perception / Q000502:physiology; D057488:Visual Prosthesis
keywords: artificial vision; neuroprosthetics; retinitis pigmentosa; subretinal visual implant