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Impressum
Testing of the surgical procedure, mechanical fixation and function of epiretinal multi-microcontact arrays in M. fascicularis
1Gerding H., 2Hornig R., 2Eckmiller R., 2Dapper M., 2Böhm S., 1Taneri S.,
1Dept. of Ophthalmology, Univ. of Muenster, 2Dept. Computer Science, Div. Neuroinformatics, Univ. of Bonn, Germany
Background: Experiments were performed to establish a sequence
of epiretinal implantation, mechanical fixation, and functional testing
by cortical recording (CR) in area V1 of epiretinal retina stimulators.
Methods: Surgery: 1. Epidural implantation of electrodes over V1
for recording of local cortical field potentials. 2. VEP recording as
initial test of CR-electrodes, 3. Pars plana vitrectomy, 4. injection
of perfluorodecalin (PFC), 5. implantation of MMAs via pars plana, 6.
epiretinal placement of MMA according to predefined coordinates, 7. stabilization
of MMAs with newly designed intrascleral hybrid microtacks (diam. <100
µm), 8. superfusion of MMAs with PFC, 9. closure of sclerotomies.
Functional testing: 9. stimulation of MMAs with biphasic, charge balanced
impulse trains, 10. multichannel recording/averaging of cortical EEP´s.
Histology: Light microscopy of contacted retina.
Results: The procedure allowed a controlled and atraumatic implantation
and fixation under the conditions necessary for permanent use of RS. The
application of hybrid microtacks proved to be very versatile and allowed
a precise spatial placement in relation to predefined retinal coordinates.
Hemorrhages did not occur following trans-retinochoroidal insertion of
microtacks. Averaged cortical EEP responses after microcontact stimulation
clearly confirmed a preservation of retinal signal transduction. Histology
of the conctacted retina revealed an atraumatic procedure.
Conclusion: MMAs as designed for definitive RSs can be implanted
and stabilized with the presented technique in a well controlled and spatially
precise procedure. Application of epiretinal stimulation and multichannel
cortical recording proved the functional integrity of contacted retina.
The signal processing used in these experiments is promising towards further
improvement of RS testing.