Methods and Perceptual Thresholds for Short-Term Electrical Stimulation of Human Retina with Microelectrode Arrays

Abstract

Threshold charge densities in severely blind patients were substantially higher than that in a normal-sighted patient. Charge densities in blind patients always exceeded one seemingly reasonable estimate of safe stimulation. The potential adversity of long-term stimulation of the retina by a prosthesis has yet to be determined.

Current and future prospects for optoelectronic retinal prostheses

“…Acute studies have been performed successfully with five patients with RP and one sighted patient. 25,26 A second German epiretinal prosthesis group, Epiret GmbH, has also recently successfully implanted a 25-electrode array (EPIRET3) into six patients over a 4-week period. 23 The implant was tolerated in five eyes with moderate post-operative inflammation, and the position of the implants remained stable until removal.…”

A Treatise of the Physical Aspects of Phosphenes and Single-Cell Selectivity in Retinal Stimulation

“…A phosphene is defined as any visual sensation represented as a spot of light in the visual field caused by methods other than stimulation of the visual system by light. Phosphenes can be elicited by mechanical forces [2], magnetic stimulation [3][4][5] or electrical stimulation [6][7][8][9][10][11][12][13][14][15].…”

“…In recent years, epi-and subretinal implants have been developed [6][7][8][9][10][11][12][13][14][15]. Humayun et al, [6][7][8][9], Mahadevappa et al, [10], Rizzo III et al, [11,12], Klauke et al, [13], Eger et al, [14] and Keserüet al, [15] and recent clinical trials [16,17] have reported that blind patients perceived sensations of spots of light while the retina was electrically stimulated.…”

“…Humayun et al, [6][7][8][9], Mahadevappa et al, [10], Rizzo III et al, [11,12], Klauke et al, [13], Eger et al, [14] and Keserüet al, [15] and recent clinical trials [16,17] have reported that blind patients perceived sensations of spots of light while the retina was electrically stimulated. These experiments clearly validated the viability of producing perception of light patterns in blind patients by electrically activating nearby retinal ganglion cells (RGCs).…”

Fabrication and Evaluation of Silicon Nanowire Photodetectors on Flexible Substrate for Retinal Prosthetic System

“…The first type, which is adopted by most of the leading groups, uses an external camera for image acquisition and processing, after which electrical signals are sent to an implanted microelectrode array, which in turn stimulates ganglion cells. (9)(10)(11)(12) The second type of retinal prosthesis uses photodiode arrays directly implanted at the retina of an eye, to provide direct ganglion cell stimulation. (13)(14)(15) The second type is preferred over the first type, since the first type requires additional functionalities, such as image acquisition, data processing and data transmission.…”