Diamond penetrating electrode array for Epi-Retinal Prosthesis

Abstract

This paper presents progress in the characterization and application of diamond penetrating electrode arrays for Epi-Retinal Prostheses. Electrical stimulation of degenerate retina has already been shown to restore partial vision for some blind patients, albeit at low spatial resolution. Higher resolution may be achievable by building arrays with electrodes that have greater areal density and closer proximity to target neurons. However, high standards of biocompatibility and hermeticity must be maintained, limiting the range of available materials of manufacture. Here, the design and histology of high density electrode arrays (approximately 100 electrodes/mm(2)) made from polycrystalline diamond and implanted into rat retinae are discussed. Results from initial steps in this process are reported.

Selectivity of direct and network-mediated stimulation of the retinal ganglion cells with epi-, sub- and intraretinal electrodes

“…To stabilize the array and ensure close proximity to the target neurons, shallow insertion of the needle electrodes into the retina was proposed (Ganesan et al 2010, Gefen 2012). Positioning of the electrodes inside IPL, however, increased the direct stimulation threshold and decreased direct selectivity by approximately a factor of 2, which might still be a better arrangement than much higher (up to a factor of 10) thresholds with electrodes floating far above the retina (Ahuja et al 2013).…”

“…In such arrangements, the electrodes can be placed in the middle of the retina, close to the inner nuclear layer (INL). Similarly, penetrating electrodes have also been proposed for epiretinal approach (Ganesan et al 2010, Gefen 2012). To assess potential advantages of intraretinal electrodes, we compared the thresholds and selectivity of direct and network-mediated stimulation with electrodes placed inside the retina (just above and just below the INL) to the thresholds measured in epiretinal and subretinal positions.…”

Prosthetic vision: devices, patient outcomes and retinal research

“…Diamond is an alternative electrode material that does not exhibit the aforementioned problems but its hardness and lack of ductility have limited its use. Recent techniques have been developed that allow the fabrication of retinal prostheses from electrically insulating polycrystalline diamond and electrically conducting nitrogen‐doped ultra‐nanocrystalline diamond (N‐UNCD) . Electrical stimulation via diamond electrodes has been shown to excite retinal ganglion cells in rat retina, thus demonstrating their viability as a material for retinal prostheses.…”

“…Recent techniques have been developed that allow the fabrication of retinal prostheses from electrically insulating polycrystalline diamond and electrically conducting nitrogendoped ultra-nanocrystalline diamond (N-UNCD). 57 Electrical stimulation via diamond electrodes has been shown to excite retinal ganglion cells in rat retina, 58 thus demonstrating their viability as a material for retinal prostheses. Electrical stimulation has been associated with retinal damage in a number of in vivo animal studies.…”

Electronic restoration of vision in those with photoreceptor degenerations

“…22 Designing an implant that uses less current to elicit a response is important as high current injection could be problematic in terms of tissue heating and damage over time. To address this distance issue some groups are testing devices with spine electrodes that penetrate into the retina 74,[87][88][89][90] This technique may be most useful for implants placed in the subretinal, suprachoroidal or episcleral space, so that they can deliver enough current to stimulate the ganglion cells. Manufacturing capability will be a determining factor for the development of electrodes that penetrate into the retina, as these electrodes would need to be much smaller (tips approximately one to 10 mm © 2012 The Authors in diameter) than currently available surface electrodes (100 to 400 mm).…”