98th Annual Meeting DOG 2000

V 167

Subretinal stimulation and cortical response (VER, SPECT) in the development of visual prosthesis in rabbit and minipig

H. G.Sachs1, K. Kobuch1, H. Schwahn2, F. Gekeler2, E. Zrenner2, V.-P. Gabel1

Purpose: To develop a subretinal visual prosthesis the proof of an consecutive cortical answer to an electric subretinal stimulation is necessary. Thus we implanted electric stimulation arrays into the subretinal space of laboratory animals.

Methods: Stimulation arrays were implanted in rabbit and Yucatan micropig via pars plana vitrectomy (ab interno) and transchorioidally (ab externo - rabbit only). By the use of foil bound stimulation electrodes the retina was stimulated out of the subretinal space. Parallel VER measurements were carried out with conventional electrodes in rabbit. The minipig VER was recorded with neurosurgical placed epidural strip electrodes. Prior to that the optical cortex of the minipig was identified by SPECT in order to gain information for the surgical access for optimal placed epidural electrodes.

Results: Implantation of stimulation electrode arrays into the subretinal space with sufficient retinal contact is possible in acute animal trials. Surgical solutions for different species were developed and applied. A reproducible recording of data of subretinal stimulation with consequent cortical activity (VER) can be obtained for both rabbit and minipig.

Conclusions: Reproducible data to proof the feasibility of a subretinal stimulation are available. The subretinal space is therefore an appropriate place for a visual prosthesis. Measurement to determine optimised stimulation parameters can be carried out with this set-up which marks an decisive point in the development of an subretinal implant.

1University Eye Clinic Regensburg, Germany; 2University Eye Clinic Tuebingen, Germany;