Operational challenges of retinal prostheses

Erich W. Schmid, Wolfgang Fink, Robert Wilke

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Two computational models for research on retinal implants are presented. In the first model, the electric field produced by a multi-electrode array in a uniform retina is calculated. It is shown how cross talk of activated electrodes and the resulting bunching of field lines in monopole and dipole activation prevent high resolution imaging with retinal implants. Furthermore, it is demonstrated how sequential stimulation and multipolar stimulation may overcome this limitation. In the second model a target volume, i.e., a probe cylinder approximating a bipolar cell, in the retina is chosen, and the passive Heaviside cable equation is solved inside this target volume to calculate the depolarization of the cell membrane. The depolarization as a function of time indicates that shorter signals stimulate better as long as the current does not change sign during stimulation of the retina, i.e., mono-phasic stimulation. Both computational models are equally applicable to epiretinal, subretinal, and suprachoroidal vision implants.

Original languageEnglish (US)
Pages (from-to)1644-1655
Number of pages12
JournalMedical Engineering and Physics
Issue number12
StatePublished - 2014
Externally publishedYes


  • Cross-talk
  • Electric current profile
  • Electric field profile
  • Electric field shaping
  • Electric stimulation
  • Epiretinal implant
  • Field line bunching
  • Phosphenes
  • Retinal prosthesis
  • Subretinal implant
  • Suprachoroidal implant

ASJC Scopus subject areas

  • Biophysics
  • Biomedical Engineering


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