97th DOG Annual Meeting 1999
IMPLANTATION OF MICROELECTRODES FOR RETINAL STIMULATION AND SIMULTANEOUS CORTICAL RECORDING IN THE CAT
L. Hesse1, T. Schanze2, B. Nebeling1, M. Wilms2, M. Eger2
For restoring a simple basic visual
perception in patients that are blind due to photoreceptor loss ganglion
cells should be stimulated by epiretinal electrodes. Therefore plane platin
microelectrodes embedded in thin polyimide film were developed.
Methods: After removal of the lens and the vitreous body a thin film
of 2 x 4 parallel arranged microelectrodes were implanted through a corneal
incision in the cat eye (n=4). The exterior part of the microelectrode film
was directed through the forehead which allowed fixation of the micro plug
at the head fixation bolt. For intraocular placement of the microelectrodes
microsurgical instruments were used. The microelectrodes were pressed at
the retinal surface by bending the microelectrode film. In 2 eyes the tip
of the electrodes were additionally glued to the retina using cyanoacrylate.
Stimulation experiments were performed between 1 to 14 days after implantation.
Success of stimulation was controlled by recording epidural and intracortical
activities (area 17/18). Microelectrodes were removed at least 3 weeks after
Results: Intraocular inflammation or retinal detachment were not
observed after implantation of the microelectrode film. Without additional
fixation the tip of the microelectrodes dislocated spontaneously. Threshold
of electrical stimulation varied between 50 and 100 µA which was tenfold
increased compared to needle electrodes used in prior experiments.
Conclusions: Intraocular implanted microelectrodes made from polyimide
were well tolerated. However, the planare configuration of the microelectrodes
required higher current pulses for stimulation which may be explained by
inadequate contact to the retinal surface. An additional fixation of the
electrodes is essential.
(Supported by BMBF, grant no. 01 IN 501 F).
1 Augenklinik, Philipps-Universität, Robert-Koch-Str. 4, D-35033 Marburg
2 AG Neurophysik, Philipps-Universität, Renthof 7, 35032 Marburg