May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Correlation of electrical detection thresholds with electrode impedance in a retinal prosthetic implant
Author Affiliations & Notes
  • M. Mahadevappa
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • J.D. Weiland
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • D. Yanai
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • R.J. Greenberg
    Second Sight LLC., Sylmar, CA
  • R. Williamson
    Second Sight LLC., Sylmar, CA
  • G.Y. Fujii
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • E. de Jaun, Jr.
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • L. LaBree
    Preventive medicine,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • M.S. Humayun
    Ophthalmology,
    Keck School of Medicine of the University of Southern California,Doheny Retina Institute,Doheny Eye Institute, Los Angeles, CA
  • Footnotes
    Commercial Relationships  M. Mahadevappa, None; J.D. Weiland, None; D. Yanai, None; R.J. Greenberg, Second Sight LLC E; R. Williamson, Second Sight LLC E; G.Y. Fujii, None; E. de Juan Jr., Second Sight LLC, CA I, P; L. LaBree, None; M.S. Humayun, Second Sight LLC I, P.
  • Footnotes
    Support  none
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 4189. doi:
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    • Get Citation

      M. Mahadevappa, J.D. Weiland, D. Yanai, R.J. Greenberg, R. Williamson, G.Y. Fujii, E. de Jaun, Jr., L. LaBree, M.S. Humayun; Correlation of electrical detection thresholds with electrode impedance in a retinal prosthetic implant . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4189.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: To study the correlation between electrical detection thresholds and electrode impedance in human epiretinal implants. Methods: The FDA and USC–IRB approved the study protocol. Informed consent was obtained and 3 subjects were implanted with a Second Sight retinal prosthesis in the worse eye. In each session electrode impedance was measured, and the patient’s detection threshold was measured by increasing stimulus current until the subject was able to see the visual percept 2 out of 3 times. Mean and standard deviations (sd) were calculated from the average impedance and threshold for both the medial (M) and the lateral (L) electrodes in the array. Comparisons between M and L means and sd's were made using paired t–tests. SAS (SAS institute, Cary NC) was used for all analyses. Results: A negative correlation was found between the impedance and threshold, i.e., as the threshold increased, the impedance decreased (by Pearson correlation coefficient as shown in table 1). This correlation was statisically significant in 3 of 6 groups. In most groups, impedance decreased with time while threshold remained statistically unchanged with time. In 2 groups threshold increased with time in a statistically significant manner and in 1 group impedance statistically unchanged. (table 1). Regression of threshold by impedance was carried out to find the slope(se) of –12.88(1.72) and adjusted R2 of 0.44(p<0.0001) in S–1. Table 1: Pearson Correlation Coefficients 

***p<0.001 **p<0.01 *p<0.05 Conclusion: A negative correlation was found between electrode impedance and threshold in all groups of electrodes in retinal implant subjects and was statiscally significant in some groups. Impedance may be a good predictor of threshold in retinal implants.

Keywords: retinal pigment epithelium • retinitis • retina 
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