title: Visual performance using a retinal prosthesis in three subjects with retinitis pigmentosa.
abstract: OBJECTIVE
  To assess visual task performance in three blind subjects implanted with epiretinal prostheses.
  
  
  METHODS
  Prospective, investigational device exemption trial.
  
  
  METHODS
  Three subjects with light perception or no light perception vision were enrolled at a single center. All subjects had retinitis pigmentosa (RP). Main inclusion criteria: light perception or worse vision in one eye and some visual experience as an adult before blindness. Main exclusion criteria included other ophthalmic problems. A prototype retinal prosthesis was implanted in the eye with worse light sensitivity. The prosthesis had 4 x 4 array of platinum electrodes tacked to the epiretinal surface. The prosthesis was wirelessly controlled by a computer or by a head-worn video camera. Visual function testing was performed in single masked or double masked fashion. Scores from the visual task were compared to chance to determine statistical significance.
  
  
  RESULTS
  The subjects performed significantly better than chance in 83% of the tests. Using the video camera, subjects scored as follows on simple visual tasks: locate and count objects (77% to 100%), differentiate three objects (63% to 73%), determine the orientation of a capital L (50% to 77%), and differentiate four directions of a moving object (40% to 90%). A subset of tests compared camera settings using multipixels vs single pixels. Using multipixel settings, subjects performed better (17%) or equivalent (83%) in accuracy and better (25%) or equivalent (75%) in reaction time.
  
  
  CONCLUSIONS
  Three RP implant subjects used epiretinal prostheses to perform simple visual tasks. Multipixel settings proved slightly more effective than single pixel settings.
authors.affiliation: Doheny Retina Institute at the Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Yanai
authors.forename: James D
authors.initials: JD
authors.lastname: Weiland
authors.forename: Manjunatha
authors.initials: M
authors.lastname: Mahadevappa
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Greenberg
authors.forename: Ione
authors.initials: I
authors.lastname: Fine
authors.forename: Mark S
authors.initials: MS
authors.lastname: Humayun
mesh_terms: D000368:Aged; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D012160:Retina / Q000502:physiology*; D012174:Retinitis Pigmentosa / Q000503:physiopathology* / Q000601:surgery*; D012815:Signal Processing, Computer-Assisted; D013647:Task Performance and Analysis; D014741:Video Recording; D014786:Vision Disorders / Q000503:physiopathology / Q000601:surgery; D014796:Visual Perception / Q000502:physiology*