Biomedical Engineering Reference
In-Depth Information
Figure 2.1. A new approach for the artificial retina 'suprachoroidal transretinal stimu-
lation (STS)'.
retina; and (2) electrical current needed to attain artificial vision by STS could
be higher than that by epi or subretinal electrode because electrodes do not
contact the retina. In order to examine the efficacy and safety of STS method,
we performed experiments on small animal (rats) and medium-sized animals
(rabbits and cats).
The procedures used on all animals conformed to the Institutional Guide-
lines of Osaka University and the ARVO Resolution on the Use of Animals in
Research.
The Effectiveness of STS in Animal Model
Artificial Vision in Royal College of Surgeons Rats
Since it has been reported in patients with RP that phosphenes can be obtained
by electrical stimulation with electrodes that are not in direct contact with the
retina, we expected that STS would be able to excite RGCs. Thus we tested
our expectations regarding the feasibility of STS for an artificial retina, by acute
electrophysiological experiments in retinal dystrophic rats (RCS rats). RCS rats
are recognized as one of the best animal models for RP. In adult RCS rats
(25
30 weeks of age) that we used, the outer retinal layers, including the
photoreceptors, were always completely degenerated, as shown in Figure 2.2a,
whereas the laminar organization of the inner retina was well preserved. Owing to
such degeneration of the outer retina, flashing light stimuli elicited no detectable
∼
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