Abstract

P 170

Temporal stability of stimulation thresholds of an epiretinal placed retina stimulator

Oliver Zeitz1, Ralf Hornig2, Matthias Keserü1, Lars Wagenfeld1, Nils Post2, Gisbert Richard1
1Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Hamburg-Eppendorf, Hamburg; 2Fa. IMI Intelligent Medical Implants GmbH, Bonn

Objective
Advances in microcomputer technology push the development of retinal stimulators forward with the ultimate aim to develop a retinal prosthesis. The aim of the present study was the characterization of threshold stability over time in an epiretinal stimulation approach.
Methods
The prototype of a wireless epiretinal retina stimulator (IMI Intelligent Medical Implants, Bonn) with 49 electrodes was implanted in two 65 year old subjects (S1 and S2) who were blind from retinitis pigmentosa. The stimulation threshold was determined by Weibull curve fits for different electrodes repetitively within the entire follow-up period.
Results
A total of 166 threshold determinations were done in both subjects during the follow-up. Average threshold was 15.1±10.9nC in S1 (N=92; follow-up 21-128 days) and 29.5±45.0nC in S2 (N=92; follow-up 27-221 days; S1 vs. S2: P<0.05). Comparing the threshold of each tested electrode within subject there were statistically similar thresholds in S1, but two electrodes with stastically different thresholds in S2. The threshold was stable over the entire study period in seven electrodes, increased slightly in two electrodes and decreased slightly in two electrodes.
Conclusions
Threshold was identified as a specific and dynamic variable for each electrode and each subject. This is a challenge for engineers designing controls of future generations of retinal stimulators that are aimed to serve as retina prosthesis.

Copyright: 2009 Porstmann Kongresse GmbH. All rights reserved. Impressum, Disclaimer.