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Liming Li, Yao Chen, Pengjia Cao, Jingjing Sun, Yiliang Lu, Xinyu Chai, Qiushi Ren; Influence Of Stimulating Modes On The Electrically Evoked Potentials Elicited By Penetrative Optic Nerve Stimulation In Rabbits. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4943.
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© ARVO (1962-2015); The Authors (2016-present)
Visual prosthesis based on penetrative optic nerve (ON) stimulation supplies an alternative approach to restore vision for blind patients suffering from untreatable degenerative retinal diseases such as RP and AMD. The influence of different stimulating modes on the electrically evoked potentials (EEP) elicited by penetrative ON stimulation has been investigated in rabbits to provide experimental evidence for more proper stimulating modes.
Craniotomy was performed on the anesthetized rabbit occipital to expose the contra-lateral visual cortex to the operated eye. Then orbital surgery was performed to expose the ON. For electrical stimulation, three linearly configured platinum-iridium wire electrodes insulated by Teflon were inserted into the ON with inter-electrode distance of 0.15 and 0.5 mm. Bipolar stimulating mode (BSM) was performed with one pair of the inserted stimulating electrodes. Monoploar stimulating mode (MSM) was performed with one stimulating electrode and one steel electrode inserted into sclera as a return one (named as individual MSM). Two stimulating electrodes activated simultaneously in MSM were also performed, which was named as simultaneous MSM. Charge-balanced cathode-first biphasic current stimuli were applied to the electrodes to stimulate the ON. The EEP were recorded with a 4 × 4 silver-ball electrode array over the visual cortex. The n represents the number of stimulating electrodes.
The experimental results showed that the thresholds of individual MSM were 39.2 ± 19.8 µA (n=10) which were significantly larger than the thresholds of simultaneous MSM (17 ± 7.4 µA, n=6) (P <0.05). There was no significant difference between the thresholds of individual MSM (24.6 ± 9.2 µA, n=6) and those of BSM with inter-electrode distance of 0.5 mm (20 ± 4.1 µA, n=3) (P =0.246). There was either no significant difference between the thresholds of individual MSM (42.1 ± 21.1 µA, n=8) and those of BSM with inter-electrode distance of 0.15 mm (47.1 ± 18 µA, n=4) (P =0.359). The spatial distribution of EEP under different stimulation mode was investigated. The results showed that the spatial extend of individual MSM and smaller spacing BSM was more restricted than that of simultaneous MSM and larger spacing BSM.
The influence of individual MSM on EEP is comparable to that of smaller spacing BSM. These two stimulating modes are better with low thresholds and small EEP spatial extend than simultaneous MSM and larger spacing BSM for the ON visual prosthesis with penetrating electrodes.
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