Direct stimulation of optic nerve by electrodes implanted in optic disc of rabbit eyes.
OBJECTIVE
To determine whether wire microelectrodes implanted in the optic disc can be used to elicit cortical potentials.


METHODS
Two or four platinum wire electrodes of two types, viz., the cut-end type and the exposed-tip type, were inserted through the vitreous and fixed in the optic disc of 16 rabbit eyes. Electrically evoked potentials (EEPs) were recorded after bipolar electrical stimulation with the two wire electrodes and by different combinations of the four-electrode system. The optic discs were examined histologically after the experiment.


RESULTS
The wire electrodes were successfully implanted and fixed into different positions of the optic disc without serious complications in all 16 eyes. EEPs could be elicited after bipolar electrical stimulation of the optic nerve using either the two-electrode system or different pairs of the four-electrode system. Threshold charge densities to elicit EEPs were 0.32-0.64 mC/cm(2) in eyes using the cut-end type of electrodes and 0.93-6.21 muC/cm(2) in eyes using the exposed-tip type. The amplitude of the EEPs increased with increasing electrical stimulus intensities. Histological evaluation revealed limited damage to the neural tissue adjacent to the electrode track.


CONCLUSIONS
The visual cortex can be activated by direct microelectrical stimulation of the optic nerve. The acute implantation of the wire microelectrodes into the optic disc by a transvitreal approach is feasible and results in only limited damage to the optic nerve.
Fang
Xiaoyun
X
Department of Ophthalmology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. fangxyp@hotmail.com
Sakaguchi
Hirokazu
H
Fujikado
Takashi
T
Osanai
Makoto
M
Kanda
Hiroyuki
H
Ikuno
Yasushi
Y
Kamei
Motohiro
M
Ohji
Masahito
M
Gan
Dekang
D
Choi
Junsub
J
Yagi
Tetsuya
T
Tano
Yasuo
Y
D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology*; D009898:Optic Disk / Q000502:physiology*; D009900:Optic Nerve / Q000502:physiology*; D011817:Rabbits; D014793:Visual Cortex / Q000502:physiology*