Retinal Prosthesis Dissertation - Student Home Pages

A Programmable Discharge Circuitry With
Current Limiting Capability for a Retinal
Prosthesis
“Biphasic stimulation is the most commonly used electrical pattern in FES (Functional
Electrical Stimulation). In such cases, a charge balanced waveform is essential to
prevent any charge accumulation in the biological tissue.”
[57]
Vision on a chip
“A “subretinal” implant uses photodiodes to replace the function of damaged
photoreceptors. The photodiodes are connected to electrodes that stimulate the
remaining neural cells in contrast; an “epiretinal” implant does not detect light but
instead uses the electrical signal from an external camera to directly stimulate the
ganglion cells’ axons, which form the optic nerve.” [32]
Specificity of Cone Connections in the Retina
and Color Vision
“… parvocellular neurons that mainly receive L-M, or M-L inputs, and in the
magnocellular neurons that receive L+M inputs? … each cone only connecting with a
one sign of input either excitatory or inhibitory” [50]
Perceptual Thresholds and Electrode Impedance
in Three Retina Prosthesis Subjects
“suggesting a complex interaction that is not completely predictable by electric field
theory…Proximity to the retina plays a role in determining the threshold and impedance
but only for electrodes that are greater than 0.5mm from the retina. Within this distance,
perception thresholds and impedances do not seem to depend on the diameter of the
electrode.” [58]