title: Transfer characteristics of subretinal visual implants: corneally recorded implant responses.
abstract: The subretinal Alpha IMS visual implant is a CE-approved medical device for restoration of visual functions in blind patients with end-stage outer retina degeneration. We present a method to test the function of the implant objectively in vivo using standard electroretinographic equipment and to assess the devices' parameter range for an optimal perception.
  
  
  
  Subretinal implant Alpha IMS (Retina Implant AG, Reutlingen, Germany) consists of 1500 photodiode-amplifier-electrode units and is implanted surgically into the subretinal space in blind retinitis pigmentosa patients. The voltages that regulate the amplifiers' sensitivity (Vgl) and gain (Vbias), related to the perception of contrast and brightness, respectively, are adjusted manually on a handheld power supply device. Corneally recorded implant responses (CRIR) to full-field illumination with long duration flashes in various implant settings for brightness gain (Vbias) and amplifiers' sensitivity (Vgl) are measured using electroretinographic setup with a Ganzfeld bowl in a protocol of increasing stimulus luminances up to 1000 cd/m2.
  
  
  
  CRIRs are a meaningful tool for assessing the transfer characteristic curves of the electronic implant in vivo monitoring the implants' voltage output as a function of log luminance in a sigmoidal shape. Changing the amplifiers' sensitivity (Vgl) shifts the curve left or right along the log luminance axis. Adjustment of the gain (Vbias) changes the maximal output. Contrast perception is only possible within the luminance range of the increasing slope of the function.
  
  
  
  The technical function of subretinal visual implants can be measured objectively using a standard electroretinographic setup. CRIRs help the patient to optimise the perception by adjusting the gain and luminance range of the device and are a useful tool for clinicians to objectively assess the function of subretinal visual implants in vivo.
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.
authors: K
authors: K
authors: Stingl
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.
authors: K U
authors: KU
authors: Bartz-Schmidt
authors: Retina Implant AG, Gerhard-Kindler-Straße 8, 72770, Reutlingen, Germany.
authors: A
authors: A
authors: Braun
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.|Klinikum Stuttgart - Katharinenhospital, Eye Clinic, Kriegsbergstraße 60, 70174, Stuttgart, Germany.
authors: F
authors: F
authors: Gekeler
authors: Retina Implant AG, Gerhard-Kindler-Straße 8, 72770, Reutlingen, Germany.
authors: U
authors: U
authors: Greppmaier
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.|Klinikum Stuttgart - Katharinenhospital, Eye Clinic, Kriegsbergstraße 60, 70174, Stuttgart, Germany.
authors: A
authors: A
authors: Schatz
authors: NMI Natural and Medical Sciences Institute at the University of Tübingen, Markwiesenstr. 55, 72770, Reutlingen, Germany.
authors: A
authors: A
authors: Stett
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.
authors: T
authors: T
authors: Strasser
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany. veronique.kitiratschky@gmail.com.
authors: V
authors: V
authors: Kitiratschky
authors: Centre for Ophthalmology, University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.|Werner Reichardt Centre for Integrative Neuroscience (CIN), University of Tübingen, Schleichstr. 12-16, 72076, Tübingen, Germany.
authors: E
authors: E
authors: Zrenner
mesh_terms: D000328:Adult; D001766:Blindness / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D003315:Cornea / Q000502:physiology*; D004567:Electrodes, Implanted; D004596:Electroretinography / Q000379:methods*; D006801:Humans; D010775:Photic Stimulation; D012160:Retina / Q000503:physiopathology; D012162:Retinal Degeneration / Q000150:complications* / Q000503:physiopathology; D014785:Vision, Ocular / Q000502:physiology*
keywords: Artificial vision; Electrophysiology; Hereditary retinal diseases; Neuroprosthetics; Retinitis pigmentosa; Subretinal visual implant