Retinal prosthesis phosphene shape analysis

Abstract

A retinal prosthesis system to restore sight for the blind is under development. The system is analogous to cochlear implants, in which photoreceptor input is bypassed and replaced by direct electrical stimulation of the retinal ganglion cells. Currently, six test subjects have been implanted with a 4x4 electrode array and stimulator. We report here psychophysical clinical data examining how stimulation amplitude affects phosphene shape and repeatability on a single electrode. Phosphene shape data was quantified by a set of numerical descriptors calculated from image moments. Comparison of phosphene descriptors for a single electrode across repeated trials and amplitude levels measured the repeatability within an amplitude group. Our experimental findings show that stimulation of the retina creates repeatable percept shapes and that an increase in stimulation amplitude causes a significant change in size and shape of phosphenes.

Augmenting intensity to enhance scene structure in prosthetic vision

“…The dynamic range of each phosphene is 8 levels. These settings were chosen to approxi mate the visual conditions of current retinal prostheses under development [8,9].…”

“…The prosthetic vision simulator used in this paper can only approximate what patients perceive with a retinal implant, and does not attempt to capture specific features and characteristics such as shape, size and duration of induced phosphenes (e.g., [23,9,8]). Rather, the SPY system provides an abstrac tion from the significant variability of these reported percep tions.…”

“…Phosphenes are typically described by patients as bright spots of light, each loosely corresponding to one stimulating elec trode. Studies have shown that the brightness and/or size of phosphenes can often increase with changes in stimulation pa rameters [8,9] . These studies show up to around 10 levels of intensity can be differentiated by implantees.…”

Spatio-Temporal Electrode Mapping and Local Interleaved Stimulation Method (STEMLIS) for Artificial Sight Systems

“…Phosphene profiles elicited by electrical stimulation are highly related to stimulation strength and stimulation duration [33][34][35]. The elicited phosphene size increases with stimulation strength.…”

Development of surgical techniques for implantation of a wireless intraocular epiretinal retina implant in Göttingen minipigs

“…A large percentage of the inner retinal neurons remains histologically intact [5], and electrical stimulation of the retina can be used to elicit phosphenes in blind individuals suffering from RP [6][7][8]. In order to restore vision in RP patients, different approaches to the development of electronic visual retinal prostheses are currently being investigated, which comprise epiretinal [6,[9][10][11][12][13], subretinal [14][15][16], transchoroidal [17], and episcleral [18] systems.…”