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

PI: Peixoto， Nathalia LProposal: 1445684题目：用于视网膜植入物安全放置的刺激电极的生物阻抗意义该项目可以为社会提供更好的理解导致失明受试者视网膜刺激电极有效性丧失的设计问题。在视网膜植入物中，刺激电极与视网膜表面之间的距离是决定感知阈值和植入物安全性的关键变量。当电极离目标神经节细胞太远时，在视网膜上达到的电流密度很低，部分原因是电流通过玻璃体扩散，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，则可能会造成机械损伤。因此，有必要确定从电极到视网膜的距离。PI建议研究可靠测量电极接近视网膜的方法，目的是建立易于转化为当前技术的技术。用于盲人的视网膜假体正在全球范围内进行临床试验，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。在视网膜表面不同位置的电极对视网膜的激活并不完全相同。刺激脉冲可以被眼壁的电阻性和容性屏障显著减弱，这在某些情况下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机械损伤的阻抗相关性，以及电介导的损伤（由于高电荷密度）。该项目的主要目标是利用目前可用的视网膜植入技术，确定植入物在原位使用期间的安全性。

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.