title: Interactions of Prosthetic and Natural Vision in Animals With Local Retinal Degeneration.
abstract: OBJECTIVE
  Prosthetic restoration of partial sensory loss leads to interactions between artificial and natural inputs. Ideally, the rehabilitation should allow perceptual fusion of the two modalities. Here we studied the interactions between normal and prosthetic vision in a rodent model of local retinal degeneration.
  
  
  METHODS
  Implantation of a photovoltaic array in the subretinal space of normally sighted rats induced local degeneration of the photoreceptors above the chip, and the inner retinal neurons in this area were electrically stimulated by the photovoltaic implant powered by near-infrared (NIR) light. We studied prosthetic and natural visually evoked potentials (VEP) in response to simultaneous stimulation by NIR and visible light patterns.
  
  
  RESULTS
  We demonstrate that electrical and natural VEPs summed linearly in the visual cortex, and both responses decreased under brighter ambient light. Responses to visible light flashes increased over 3 orders of magnitude of contrast (flash/background), while for electrical stimulation the contrast range was limited to 1 order of magnitude. The maximum amplitude of the prosthetic VEP was three times lower than the maximum response to a visible flash over the same area on the retina.
  
  
  CONCLUSIONS
  Ambient light affects prosthetic responses, albeit much less than responses to visible stimuli. Prosthetic representation of contrast in the visual scene can be encoded, to a limited extent, by the appropriately calibrated stimulus intensity, which also depends on the ambient light conditions. Such calibration will be important for patients combining central prosthetic vision with natural peripheral sight, such as in age-related macular degeneration.
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States 2Department of Ophthalmology, Stanford University, Stanford, California, United States.
authors.forename: Henri
authors.initials: H
authors.lastname: Lorach
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Lei
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, United States.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Galambos
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, United States.
authors.forename: Theodore
authors.initials: T
authors.lastname: Kamins
authors.affiliation: Institute of Photonics, University of Strathclyde, Glasgow, Scotland, United Kingdom.
authors.forename: Keith
authors.initials: K
authors.lastname: Mathieson
authors.affiliation: Department of Ophthalmology, Stanford University, Stanford, California, United States.
authors.forename: Roopa
authors.initials: R
authors.lastname: Dalal
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States 2Department of Ophthalmology, Stanford University, Stanford, California, United States.
authors.forename: Philip
authors.initials: P
authors.lastname: Huie
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California, United States.
authors.forename: James
authors.initials: J
authors.lastname: Harris
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States 2Department of Ophthalmology, Stanford University, Stanford, California, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Palanker
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology; D010775:Photic Stimulation; D011474:Prosthesis Design; D051381:Rats; D020318:Rats, Long-Evans; D012162:Retinal Degeneration / Q000503:physiopathology / Q000601:surgery*; D057488:Visual Prosthesis