Advertisement

Findings from Acute Retinal Stimulation in Blind Patients

  • Peter Walter
  • Gernot Roessler
Chapter

Abstract

In acute retinal stimulation experiments retinal stimulators are inserted into the eye, activated, and responses from patients to electrical stimulation are recorded. These tests were done to obtain evidence that the principle of electrical stimulation of the retina works in terms of elicitation of phosphenes or visual perception, respectively. These tests were also done to narrow the parameter range for electrode size and stimulation energy before efforts were undertaken to fabricate a device for chronic stimulation. Results from such tests were also helpful to describe possible perception patterns of patients and also to estimate possible visual acuities after implantation. Usually these tests were done in local anaesthesia so that the patient can respond verbally or by means of an interface to the stimulation. In different experiments rheobase and chronaxie data were reported showing a large variation depending on the device and on individual factors such as the disease state or the proximity between the electrode and the retina. Possible spatial and temporal resolution data were calculated from such experiments demonstrating that the concept of retinal stimulation in blind RP subjects can really help to restore some useful visual function in such patients.

Keywords

Retinitis Pigmentosa Electrode Array Visual Response Retinal Surface Normal Retina 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

DTL

Dawson Trick, Litzkow

I

Intensity e.g. current for stimulation

LP

Light probe

MUX

Multiplexer

PC

Computer system

PS

Power source

RCS

Royal College of Surgeons

RI

Response interface

RP

Retinitis pigmentosa

SIU

Stimulus isolation unit

STIM

Stimulator

T

Time

VD

Video documentation

References

  1. 1.
    Brindley GS, Lewin WS (1968), The sensations produced by electrical stimulation of the visual cortex. J Physiol 196: p. 479–493.Google Scholar
  2. 2.
    Cha K, Horch KW, Norman RA (1992), Simulation of a phosphene based visual field: visual acuity in a pixelized vision system. Ann Biomed Eng 20: p. 439–449.CrossRefGoogle Scholar
  3. 3.
    Chen SJ, Mahadeveppa M, Roizenblatt R et al (2006), Neural responses elicited by electrical stimulation of the retina. Trans Am Ophthalmol Soc 104: p. 252–259.Google Scholar
  4. 4.
    Delbeke J, Pins D, Michaux G et al (2001), Electrical stimulation of anterior visual pathways in retinitis pigmentosa. Invest Ophthalmol Vis Sci 42: p. 291–297.Google Scholar
  5. 5.
    Dobelle WH, Mladejovsky MG (1974), Phosphenes produced by electrical stimulation of human occipital cortex, and their application to the development of a prosthesis for the blind. J Physiol 243(2): p. 553–576.Google Scholar
  6. 6.
    Eckhorn R, Wilms H, Schanze T et al (2006), Visual resolution with retinal implants estimated from recordings in cat visual cortex. Vision Res 46: p. 2675–2690.CrossRefGoogle Scholar
  7. 7.
    Gekeler F, Kobuch G, Schwahn HN et al (2004), Subretinal electrical stimulation of the rabbit retina with acutely implanted electrode arrays. Graefes Arch Clin Exp Ophthalmol 242(7): p. 587–596.CrossRefGoogle Scholar
  8. 8.
    Gekeler F, Messias A, Ottinger M et al (2006), Phosphenes electrically evoked with DTL electrodes: a study in patients with retinitis pigmentosa, glaucoma, and homonymous visual field loss and normal subjects. Invest Ophthalmol Vis Sci 47: p. 4966–4974.CrossRefGoogle Scholar
  9. 9.
    Hesse L, Schanze T, Wilms H et al (2000), Implantation of retina stimulation electrodes and recording of electrical stimulation responses in the visual cortex of the cat. Graefes Arch Clin Exp Ophthalmol 238: p. 840–845.CrossRefGoogle Scholar
  10. 10.
    Hornig R, Laube T, Walter P et al (2005), A method and technical equipment for an acute human trial to evaluate retinal implant technology. J Neural Eng 2: p. S129–S134.CrossRefGoogle Scholar
  11. 11.
    Humayun MS, deJuan E (1998), Artificial vision. Eye 12: p. 605–607.Google Scholar
  12. 12.
    Humayun MS, deJuan E, Dagnelie G et al (1996), Visual perception elicited by electrical stimulation of the retina in blind humans. Arch Ophthalmol 114: p. 40–46.Google Scholar
  13. 13.
    Humayun MS, deJuan E, Weiland JD et al (1999), Pattern electrical stimulation of the human retina. Vision Res 39: p. 2569–2576.CrossRefGoogle Scholar
  14. 14.
    Rizzo JF, Wyatt J, Loewenstein J et al (2003), Methods and perceptual thresholds for short term electrical stimulation of human retina with microelectrode arrays. Invest Ophthalmol Vis Sci 44: p. 5355–5361.CrossRefGoogle Scholar
  15. 15.
    Rizzo JF, Wyatt J, Loewenstein J et al (2003), Perceptual efficacy of electrical stimulation of human retina with a microelectrode array during short term surgical trials. Invest Ophthalmol Vis Sci 44: p. 5362–5369.CrossRefGoogle Scholar
  16. 16.
    Sachs HG, Gekeler F, Schwahn HN et al (2005), Implantation of stimulation electrodes in the subretinal space to demonstrate cortical responses in Yucatan minipig in the course of visual prosthetics development. Eur J Ophthalmol 4: p. 493–499.Google Scholar
  17. 17.
    Walter P, Heimann K (2000), Evoked cortical potentials after electrical stimulation of the inner retina in rabbits. Graefes Arch Clin Exp Ophthalmol 238: p. 315–318.CrossRefGoogle Scholar
  18. 18.
    Walter P, Kisvarday Z, Goertz M et al (2005), Cortical activation via an implanted wireless retinal prosthesis. Invest Ophthalmol Vis Sci 46: p. 1780–1785.CrossRefGoogle Scholar
  19. 19.
    Weiland JD, Humayun MS, Dagnelie G et al (1999), Understanding the origin of visual percepts elicited by electrical stimulation of the human retina. Graefes Arch Clin Exp Ophthalmol 237: p. 1007–1013.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Department of OphthalmologyRWTH Aachen UniversityAachenGermany

Personalised recommendations