title: Electrically evoked electroretinograms and pupil responses in Argus II retinal implant wearers.
abstract: OBJECTIVE
  We have recorded the electrically evoked electroretinogram (eERG) and flash ERG in Argus II retinal prosthesis wearers with end-stage retinitis pigmentosa to estimate response properties of the degenerated inner retina to local electrical stimulation. In addition, we have recorded pupil diameters during electrical stimulation.
  
  
  METHODS
  Raw corneal eERGs were recorded at multiple stimulus levels in three subjects. eERG signals were heavily contaminated with various artifacts, including switching artifacts generated by the implant electronics, stimulus, blink, and eye-movement artifacts. Pupil responses were recorded in one subject using a pupil tracker.
  
  
  RESULTS
  eERGs were decontaminated by a variety of techniques, including wavelet transformation and response averaging. The dominant component was a negative wave peaking at approximately 200 ms. eERG amplitudes correlated significantly with stimulus level, but peak latencies did not correlate with stimulus level. Pupil constriction correlated significantly with stimulus level and pupil responses could be accurately used to estimate subjective threshold.
  
  
  CONCLUSIONS
  eERG recordings hold the potential to be developed further for use as a diagnostic tool for retinal implants. A straightforward approach to increase eERG amplitudes would be the development of intraocular recording methods based on reverse telemetry. The robust pupil response to electrical stimulation in one subject indicates that pupillography can be exploited to assess implant functionality, but reliable pupil recordings could not be obtained in all subjects.
authors.affiliation: Department of Ophthalmology, Johns Hopkins University, Baltimore, MD, USA. h.c.stronks@lumc.nl.|Computer Vision Research Group, NICTA, Canberra, Australia. h.c.stronks@lumc.nl.|Department of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia. h.c.stronks@lumc.nl.
authors.forename: H Christiaan
authors.initials: HC
authors.lastname: Stronks
authors.affiliation: Department of Ophthalmology, Johns Hopkins University, Baltimore, MD, USA.|Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Barry
authors.affiliation: Department of Ophthalmology, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Gislin
authors.initials: G
authors.lastname: Dagnelie
mesh_terms: D000328:Adult; D016477:Artifacts; D004558:Electric Stimulation; D004596:Electroretinography; D006801:Humans; D008027:Light; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage; D010775:Photic Stimulation; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D012160:Retina / Q000503:physiopathology*; D012174:Retinitis Pigmentosa / Q000503:physiopathology* / Q000628:therapy*; D057488:Visual Prosthesis
chemical_list: D009184:Mydriatics
keywords: Argus II; Electrical stimulation; Electrophysiology; Electroretinogram; Pupil tracking; Pupillography; Retinal implant