Phosphene Vision Simulator

A camera built into a pair of glasses captures the world in real time, effectively replacing the function of the natural eye.

An external processor simplifies the video into a grid of average brightness values that matches the layout of the implanted electrode array. Each square in the grid controls the electrical current sent to one electrode.

The electrodes stimulate neurons in the visual cortex (V1) using currents between 2 and 77 microamps (μA). Lower currents create faint spots of light (phosphenes), while higher currents create brighter ones.

By converting brightness in each part of the image into a specific current level, the system turns the visual scene into a pattern of electrical signals that the brain can understand.

This shows what a visually impaired person using a cortical prosthesis might see. Each dot is a phosphene, which is a small spot of light created by stimulating neurons in the V1 area of the occipital lobe.

Unlike normal vision, this type of vision is made up of separate points of light instead of a smooth, continuous image.

This simulates the areas of the brain being stimulated and the level of stimulation used to create the phosphene pattern. It is important to note that every brain is different, so this mapping is not universal.

Each pixel in the V1 region is matched to a specific cell in the camera grid using retinotopic coordinates. This mapping is based on three main principles: eccentricity, contralateral projection, and vertical inversion.

Eccentricity describes how visual information moves from the fovea at the occipital pole to the peripheral vision at the medial edge. The fovea occupies a larger area of the cortex because it processes fine detail. This follows a log-polar pattern of cortical magnification.

Contralateral projection means that the left visual cortex represents the right visual field, and the right visual cortex represents the left visual field.

Vertical inversion means that the upper part of V1 corresponds to the lower visual field, while the lower part of V1 corresponds to the upper visual field.