title: Importance of eye position on spatial localization in blind subjects wearing an Argus II retinal prosthesis.
abstract: OBJECTIVE
  With a retinal prosthesis connected to a head-mounted camera (camera-connected prosthesis [CC-P]), subjects explore the visual environment through head-scanning movements. As eye and camera misalignment might alter the spatial localization of images generated by the device, we investigated if such misalignment occurs in blind subjects wearing a CC-P and whether it impacts spatial localization, even years after the implantation.
  
  
  METHODS
  We studied three subjects blinded by retinitis pigmentosa, fitted with a CC-P (Argus II) 4 years earlier. Eye/head movements were video recorded as subjects tried to localize a visual target. Pointing coordinates were collected as subjects were requested to orient their gaze toward predetermined directions, and to point their finger to the corresponding perceived spot locations on a touch screen. Finally, subjects were asked to give a history of their everyday behavior while performing visually controlled grasping tasks.
  
  
  RESULTS
  Misaligned head and gaze directions occurred in all subjects during free visual search. Pointing coordinates were collected in two subjects and showed that median pointing directions shifted toward gaze direction. Reportedly all subjects were unable to accurately determine their eye position, and they developed adapted strategies to perform visually directed movements.
  
  
  CONCLUSIONS
  Eye position affected perceptual localization of images generated by the Argus II prosthesis, and consequently visuomotor coordination, even 4 years following implantation. Affected individuals developed strategies for visually guided movements to attenuate the impact of eye and head misalignment. Our observations provide indications for rehabilitation procedures and for the design of upcoming retinal prostheses. (ClinicalTrials.gov number, NCT00407602.).
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France.
authors.forename: Norman
authors.initials: N
authors.lastname: Sabbah
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France.
authors.forename: Colas N
authors.initials: CN
authors.lastname: Authié
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France.
authors.forename: Nicolae
authors.initials: N
authors.lastname: Sanda
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France.
authors.forename: Saddek
authors.initials: S
authors.lastname: Mohand-Said
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France.
authors.forename: José-Alain
authors.initials: JA
authors.lastname: Sahel
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR S968, Institut de la Vision, Paris, France Department of Clinical Neurosciences, Geneva University School of Medicine, Geneva, Switzerland.
authors.forename: Avinoam B
authors.initials: AB
authors.lastname: Safran
mesh_terms: D001766:Blindness / Q000503:physiopathology* / Q000601:surgery; D002138:Calibration; D005133:Eye Movements / Q000502:physiology*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009048:Motor Skills / Q000502:physiology; D009068:Movement / Q000502:physiology; D012174:Retinitis Pigmentosa / Q000150:complications / Q000503:physiopathology; D013028:Space Perception / Q000502:physiology*; D057488:Visual Prosthesis
keywords: eye movements; retinal prostheses; spatial localization