Retinal Prosthesis Phosphene Perception — 2D Field Map

Electrode Stimulation

Current amplitude 250 µA

Electrode eccentricity 2.0 mm

Pulse frequency 40 Hz

Show current-density field

Readouts

Activated tissue radius

0.00 mm

Perceived phosphene size

0.00°

Perceived brightness

How it works

This is the same epiretinal-implant model as the 3D version, re-plotted as two native 2D charts instead of a rotating scene. The left panel is a simulated scalar field on a flattened retinal map (a tangent-plane "fundus map", the same projection ophthalmologists use) — current density is computed on an 80×80 grid and colour-mapped, with a contour line traced exactly where it crosses the activation threshold:

density(x,y) = I − k·d²,   d = distance from electrode (mm)
r(I) = sqrt( max(0, I − I_th) / k )   ← threshold contour radius
I_th ≈ 80 µA,  k ≈ 80 µA/mm²

The quadratic falloff is constructed so its threshold crossing lands exactly on the same activated-tissue radius the clinical current-spread relation predicts — the field is a genuine grid computation, not a decorative gradient.

The right panel is a 2D perceived-visual-field chart: eccentricity is converted to visual degrees by the retina's magnification factor, and the phosphene is drawn as a disc of the resulting angular size:

mm/deg(e) = M0 / (e + E2)
size(deg) = 2r / mm/deg(e)

A third inset is a brightness-vs-frequency parameter curve — brightness saturates with pulse frequency, and the current operating point is marked on the curve live:

brightness(f) = 100% · (1 − e^(−f / f0)),  f0 ≈ 20 Hz

Current amplitude — expands the current-density field and the threshold contour on the retinal map.
Electrode eccentricity — slides the electrode outward on the retinal map and moves/rescales the phosphene in the visual-field chart.
Pulse frequency — drives the brightness readout, the pulsing electrode marker, and the marker's position on the brightness curve.

Retinal current-density mapPerceived visual field

Active electrode Inactive electrodes Phosphene