title: Performance of photovoltaic arrays in-vivo and characteristics of prosthetic vision in animals with retinal degeneration.
abstract: Loss of photoreceptors during retinal degeneration leads to blindness, but information can be reintroduced into the visual system using electrical stimulation of the remaining retinal neurons. Subretinal photovoltaic arrays convert pulsed illumination into pulsed electric current to stimulate the inner retinal neurons. Since required irradiance exceeds the natural luminance levels, an invisible near-infrared (915 nm) light is used to avoid photophobic effects. We characterized the thresholds and dynamic range of cortical responses to prosthetic stimulation with arrays of various pixel sizes and with different number of photodiodes. Stimulation thresholds for devices with 140 μm pixels were approximately half those of 70 μm pixels, and with both pixel sizes, thresholds were lower with 2 diodes than with 3 diodes per pixel. In all cases these thresholds were more than two orders of magnitude below the ocular safety limit. At high stimulation frequencies (>20 Hz), the cortical response exhibited flicker fusion. Over one order of magnitude of dynamic range could be achieved by varying either pulse duration or irradiance. However, contrast sensitivity was very limited. Cortical responses could be detected even with only a few illuminated pixels. Finally, we demonstrate that recording of the corneal electric potential in response to patterned illumination of the subretinal arrays allows monitoring the current produced by each pixel, and thereby assessing the changes in the implant performance over time.
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA; Institut de la Vision, Paris 75012, France. Electronic address: henri.lorach@gmail.com.
authors.forename: Henri
authors.initials: H
authors.lastname: Lorach
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Georges
authors.initials: G
authors.lastname: Goetz
authors.affiliation: Faculty of Life Sciences, Bar-Ilan University Ramat-Gan, 5290002, Israel.
authors.forename: Yossi
authors.initials: Y
authors.lastname: Mandel
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Lei
authors.affiliation: Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA
authors.forename: Ludwig
authors.initials: L
authors.lastname: Galambos
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Theodore I
authors.initials: TI
authors.lastname: Kamins
authors.affiliation: Institute of Photonics, University of Strathclyde, Scotland, UK.
authors.forename: Keith
authors.initials: K
authors.lastname: Mathieson
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Huie
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Roopa
authors.initials: R
authors.lastname: Dalal
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Harris
authors.affiliation: Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Palanker
mesh_terms: D000818:Animals; D001766:Blindness / Q000209:etiology / Q000534:rehabilitation*; D015350:Contrast Sensitivity / Q000502:physiology; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology; D010775:Photic Stimulation; D051381:Rats; D012160:Retina / Q000502:physiology; D012162:Retinal Degeneration / Q000150:complications / Q000503:physiopathology*; D014793:Visual Cortex / Q000502:physiology*; D057488:Visual Prosthesis
keywords: Prosthetic vision; Rat; Subretinal implant; Visually evoked potentials