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Han Mingsong, Yujing Bai, Zhi Chen, Yao Chen, Heng Miao, Juan Hu, Yu Zhao; Efficacy of A Newly Developed Retinal Prosthesis System 60 in Cat. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4567.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal Prosthesis System 60 (RPS60) is designed to elicit phosphene by stimulating retinal ganglion cells (RGCs) in subjects of severe to profound blindness due to outer retinal degeneration. The RPS60 consists of 60 electrodes with simplified structure and wide stimulation pulse width. In vivo studies on cats were performed to evaluate the effectiveness of RPS60 in eliciting cortical potentials.
Three adult cats were used in current study. Their right eyes were surgically implanted with RPS 60, whereas the contralateral eyes were used as control. After implantation, the skulls above V1 cortical layers were carefully removed, and 8-channel cortical recording electrodes were placed securely on the left brain. Electrically evoked potentials (EEPs) in response to RPS 60 were recorded from V1 cortical with 3x5 silver-ball electrode, and their physiological properties were studied 60 minutes after implantation. Different currents (100 uA, 200 uA, 300 uA, 400 uA, 500 uA) and pulse widths (1ms, 3ms, 9ms) were applied to the electrodes. In addition, 1-channel, 2-channel, and 4-channel tests were also performed. To eliminate the influence of stray currents, EEPs were recorded from cats before and after surgery.
EEPs were successfully elicited by RPS60. The threshold intensity (C) of the EEP response to RPS60 was approximately 0.26mC/cm2 in normal cats. Stimulation currents are negatively correlated to P1, but correlated positively to the potentials in a linear fashion. Stimulating pulse width positively correlates with N1, P1 and more notedly, has a disproportionally positive correlation with the potential’s amplitude. Similar disproportionally positive correlation is observed between the number of stimulus channels and the potentials. The topological corresponding relations between the retina and cortical were also proved.
The elicitation of EEPs by RPS60 from the retina suggests RPS60 is useful in patients with outer retinal damage. The long-term safety and efficacy studies are needed for further evaluation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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