No abstract

In the last decade several groups have been developing vision prostheses to restore visual perception to the profoundly blind. Despite some promising results from human trials, further understanding of the neural mechanisms involved is crucial for improving the efficacy of these devices. One of the techniques involves placing stimulating electrodes in the subretinal space between the photoreceptor layer and the pigment epithelium to evoke neural responses in the degenerative retina. This study used cell-attached and whole cell current-clamp recordings to investigate the responses of rabbit retinal ganglion cells (RGCs) following subretinal stimulation with 25-mum-diameter electrodes. We found that direct RGC responses with short latency (

These studies demonstrate that PEDOT can be produced as a stable electrode coating which can be sterilized and perform effectively and safely in neuroprosthetic applications. Furthermore these findings address the necessity for characterizing in vitro properties of electrodes in biologically relevant milieu which mimic the in vivo environment more closely.

With increasing research advances and clinical trials of visual prostheses, there is significant demand to better understand the perceptual and psychophysical aspects of prosthetic vision. In prosthetic vision a visual scene is composed of relatively large, isolated, spots of light so-called "phosphenes", very much like a magnified pictorial print. The utility of prosthetic vision has been studied by investigators in the form of virtual-reality visual models (simulations) of prosthetic vision administered to normally sighted subjects. In this review, the simulations from these investigations are examined with respect to how they visually render the phosphenes and the virtual-reality apparatus involved. A comparison is made between these simulations and the actual descriptions of phosphenes reported from human trials of visual prosthesis devices. For the results from these simulation studies to be relevant to the experience of visual prosthesis recipients, it is important that, the simulated phosphenes must be consistent with the descriptions from human trials. A standardized simulation and reporting framework is proposed so that future simulations may be configured to be more realistic to the experience of implant recipients, and the simulation parameters from different investigators may be more readily extracted, and study results more fittingly compared.

A new method for fabrication of microelectrode arrays comprised of traditional implant materials is presented. The main construction principle is the use of spun-on medical grade silicone rubber as insulating substrate material and platinum foil as conductor (tracks, pads and electrodes). The silicone rubber and the platinum foil are patterned by laser cutting using an Nd:YAG laser and a microcontroller-driven, stepper-motor operated x-y table. The method does not require expensive clean room facilities and offers an extremely short design-to-prototype time of below 1 day. First prototypes demonstrate a minimal achievable feature size of about 30 microm.