NSF/FDA SIR: Bioimpedance of stimulating electrodes for the safe placement of retinal implants

PI：Peixoto，Nathalia LProposal：1445684标题：用于安全放置视网膜植入物的刺激电极的生物阻抗意义这个项目可能会让社会更好地了解导致盲人受试者视网膜刺激电极失去有效性的设计问题。在视网膜植入物中，刺激电极和视网膜表面之间的距离是确定感知阈值和植入物安全性的关键变量。当电极距离目标神经节细胞太远时，视网膜中获得的电流密度很低，部分原因是电流通过玻璃体体液传播，从而提高了感知阈值，从而降低了空间分辨率。另一方面，如果电极接触到视网膜，机械损伤是可以预见的。因此，需要确定电极到原位视网膜的距离。国际盲人联合会建议研究可靠地测量电极接近视网膜的方法，目的是建立易于翻译到当前技术的技术。技术说明用于盲人的视网膜假体正在世界各地进行临床试验，包括FDA批准的Argus II假体。每个视网膜假体都试图将刺激电极阵列放置在靠近视网膜的位置，以便有效地激活剩余的视网膜神经回路。视网膜表面不同位置的电极激活视网膜并不完全相同。刺激脉冲可以被眼壁中的阻性和电容性屏障显著减弱，在某些情况下，这可能会阻止视网膜组织的有效激活。在这里，我们计划研究刺激电极对视网膜内部的机械损伤以及电介导的损伤(由于高电荷密度)的阻抗相关性。该项目的主要目标是利用目前视网膜植入物的现有技术，在原位确定植入物使用期间的安全性。

PI: Peixoto, Nathalia LProposal: 1445684Title: Bioimpedance of stimulating electrodes for the safe placement of retinal implantsSignificanceThis project may provide society are a better understanding of the design issues that cause a loss of effectiveness of retinal stimulus electrodes in blind subjects. In retinal implants, the distance between the stimulating electrode and the surface of the retina is a critical variable for determining perceptual thresholds and for implant safety in general. When the electrode is too far from the target ganglion cells, the current density achieved in the retina is low, in part due to current spreading through the vitreous humour, thus raising the perceptual threshold and therefore decreasing spatial resolution. If, on the other hand, the electrode touches the retina, mechanical damage can be expected. There is therefore a need to determine the distance from the electrode to the retina in situ. The PI proposes to investigate methods to reliably measure electrode proximity to the retina, with the objective of establishing techniques which are readily translatable to current technology.Technical DescriptionRetinal prostheses for the blind are in clinical trials worldwide, including the FDA-approved Argus II prosthesis. Each retinal prosthesis attempts to position stimulus electrode arrays in close proximity to the retina in order to effectively activate the remaining retinal neural circuitry. Retinal activation by electrodes in different locations on the retinal surface are not all equivalent. Stimulus pulses can be markedly attenuated by resistive and capacitive barriers in the eyewall, which in some cases could prevent effective activation of the retinal tissue. Here we plan to investigate the impedance correlates of mechanical damage to the inner retina by the stimulus electrodes, as well as electrically-mediated damage (due to high charge density). The main objective of this project is to determine safety throughout the period when the implant is used, in situ, leveraging currently available technology for retinal implants.