title: Spatial resolution and perception of patterns mediated by a subretinal 16-electrode array in patients blinded by hereditary retinal dystrophies.
abstract: OBJECTIVE
  The perception of 11 persons blinded by hereditary retinal degeneration elicited by a subretinally implanted 16-electrode array used for light-independent direct stimulation of the retina is described. This device is part of the Tübingen retina implant, which also employs a light-sensitive, multiphotodiode array (MPDA). The ability to reliably recognize complex spatial percepts was investigated.
  
  
  METHODS
  Eleven blind volunteers received implants and participated in standardized psychophysical tests investigating the size and shape of perceptions elicited by single-electrode activation, multiple-electrode activation, and activation of compound patterns such as simplified letters.
  
  
  RESULTS
  Visual percepts were elicited reliably in 8 of 11 patients. On single-electrode activation, percepts were generally described as round spots of light of distinguishable localization in the visual field. On activation of a pattern of electrodes, percepts matched that pattern when electrodes were activated sequentially. Patterns such as horizontal or vertical bars were identified reliably; the most recent participant was able to recognize simplified letters presented on the 16-electrode array. The smallest distance between sites of concurrent retinal stimulation still yielding discernible spots of light was assessed to be 280 μm, corresponding to a logMAR of 1.78.
  
  
  CONCLUSIONS
  Subretinal electric stimulation can yield reliable, predictable percepts. Patterned perception is feasible, enabling blind persons to recognize shapes and discriminate different letters. Stimulation paradigms must be optimized, to further increase spatial resolution, demanding a better understanding of physical and biological effects of single versus repetitive stimulation (ClinicalTrials.gov number, NCT00515814).
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Tübingen, Germany. robert.wilke@med.uni-tuebingen.de
authors.forename: Robert
authors.initials: R
authors.lastname: Wilke
authors.forename: Veit-Peter
authors.initials: VP
authors.lastname: Gabel
authors.forename: Helmut
authors.initials: H
authors.lastname: Sachs
authors.forename: Karl-Ulrich
authors.initials: KU
authors.lastname: Bartz Schmidt
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.forename: Dorothea
authors.initials: D
authors.lastname: Besch
authors.forename: Peter
authors.initials: P
authors.lastname: Szurman
authors.forename: Alfred
authors.initials: A
authors.lastname: Stett
authors.forename: Barbara
authors.initials: B
authors.lastname: Wilhelm
authors.forename: Tobias
authors.initials: T
authors.lastname: Peters
authors.forename: Alex
authors.initials: A
authors.lastname: Harscher
authors.forename: Udo
authors.initials: U
authors.lastname: Greppmaier
authors.forename: Steffen
authors.initials: S
authors.lastname: Kibbel
authors.forename: Heval
authors.initials: H
authors.lastname: Benav
authors.forename: Anna
authors.initials: A
authors.lastname: Bruckmann
authors.forename: Katarina
authors.initials: K
authors.lastname: Stingl
authors.forename: Akos
authors.initials: A
authors.lastname: Kusnyerik
authors.forename: Eberhart
authors.initials: E
authors.lastname: Zrenner
mesh_terms: D000328:Adult; D001766:Blindness / Q000534:rehabilitation / Q000601:surgery*; D004567:Electrodes, Implanted; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception; D009949:Orientation; D010364:Pattern Recognition, Visual; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods; D011601:Psychophysics; D058499:Retinal Dystrophies / Q000534:rehabilitation / Q000601:surgery*; D013028:Space Perception; D057488:Visual Prosthesis