Chowdhury Vivek, Morley John W, Coroneo Minas T
Department of Ophthalmology, Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia.
J Clin Neurosci. 2008 Aug;15(8):900-6. doi: 10.1016/j.jocn.2007.08.012.
Electrical stimulation of the retina with extraocular electrodes is a new approach to developing a retinal prosthesis for blind patients. We have evaluated stimulus and electrode configurations for an extraocular retinal prosthesis (ERP). In anesthetized cats, ERP disc electrodes of 1 mm, 2 mm and 3 mm diameter were sutured to the sclera over the lateral globe. Electrically evoked potentials (EEPs) were recorded over the ipsilateral visual cortex, which resulted from the retinal stimulation of the ERP electrodes with a return electrode placed at the medial canthus. Square pulses, triangular pulses and the effects of dark adaptation and electrode size on the amplitude and thresholds for a cortical response were investigated. Square pulses were more effective than triangular pulses for stimulating the retina. Dark adaptation leads to a large increase in the threshold for retinal stimulation. There was no difference in the threshold for stimulation between electrodes of 1 mm and 3 mm diameter. Stimulation of the retina with extraocular electrodes elicits an EEP that is similar to that generated by retinal stimulation with intraocular electrodes. The use of square pulses is preferred to triangular pulses to minimize the peak current density at the electrode-tissue interface. As there is little difference in the threshold current for retinal stimulation with 1 mm or 3 mm electrodes, 3 mm electrodes are preferred as this will decrease the charge density at the active surface of the electrode.
用眼外电极对视网膜进行电刺激是为盲人患者开发视网膜假体的一种新方法。我们已经评估了用于眼外视网膜假体（ERP）的刺激和电极配置。在麻醉的猫中，将直径为1毫米、2毫米和3毫米的ERP圆盘电极缝合到眼球外侧的巩膜上。在同侧视觉皮层记录电诱发电位（EEP），这是由眼外视网膜假体电极刺激视网膜并将返回电极置于内眦处产生的。研究了方波脉冲、三角波脉冲以及暗适应和电极尺寸对皮层反应的幅度和阈值的影响。方波脉冲在刺激视网膜方面比方波脉冲更有效。暗适应导致视网膜刺激阈值大幅增加。直径为1毫米和3毫米的电极在刺激阈值上没有差异。用眼外电极刺激视网膜会引发一种EEP，它类似于用眼内电极刺激视网膜所产生的EEP。为了使电极 - 组织界面处的峰值电流密度最小化，首选方波脉冲而非三角波脉冲。由于1毫米或3毫米电极刺激视网膜的阈值电流差异不大，因此首选3毫米电极，因为这将降低电极活性表面的电荷密度。
