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Chuanqing Zhou, Xinyu Chai, Yao Chen, Xun Cao, Qing Lyu; Effects of different three-dimensional electrodes on epiretinal electrical stimulation by modeling analysis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):779.
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The objective of this study was to investigate the effects of different three-dimensional electrodes placed at epiretinal space on the excitation of retinal ganglion cells (RGCs) by computational modeling analysis.
The 3-D finite element models of retinal electrical stimulation were established, consisting of the platinum microelectrode, vitreous body, multi-layered retina, and retinitis epithelium (RPE). Different three-dimensional models of disk and non-planar electrodes were used in the epiretinal electrical stimulation. Multi RGCs including somas and axons were modelled using NEURON software to study the responses of RGCs under electrical stimulation by different-type electrodes. Threshold current, threshold charge density and RGCs activated area were the three key factors to evaluate the performance of stimulating electrodes. Threshold current or threshold charge density was defined as the minimum stimulating current or charge density which can activate only one RGC in our model. RGCs activated area represented the region of activated RGCs under a certain stimulating current.
With the increment of distance between disk electrode and retina, both threshold currents and threshold charge density showed approximately linear relationship with the distance increasing. With the increment of diameter of the disk electrode, threshold current increased while threshold charge density decreased. Non-planar electrodes could provoke different activation responses of RGCs compared with disk electrodes. Concave electrodes performed superior stimulation localization and electrode safety, while convex electrodes acted relatively poor.
The combination of finite element analysis and NEURON software provides an efficient way to evaluate the influences of various 3-D electrodes on epiretinal electrical stimulation. Non-planar electrodes had larger threshold currents than the disk one. Among the five types of electrodes, concave spherical electrode might be the ideal candidate considering the good stimulation localization and electrode safety.
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