Cortical visual prosthesis

Writes phosphenes by stimulating primary visual cortex (V1) directly, bypassing the entire eye and optic nerve. It is the only route for blindness caused by glaucoma, optic-nerve damage, or eye loss, but it demands penetrating or surface electrode arrays on the brain and confronts cortical magnification and long-term stability challenges.

Modern intracortical efforts (CORTIVIS/Fernandez, the Illinois ICVP, Utrecht/NIN high-count animal work) use Utah-style penetrating arrays to elicit small, dense phosphenes and have shown letter and simple-shape recognition from multi-electrode patterns; a landmark animal study drove over a thousand electrodes to write recognizable characters. Surface arrays (e.g. Orion) are safer but give larger, sparser phosphenes.

Other pathway targets between retina and cortex, such as optic-nerve cuff electrodes (OpticSELINE) and lateral-geniculate (thalamic) microstimulation, remain experimental alternatives.