Prosthetic Vision

In the 1960s, Giles S. Brindley of the Univ. of Cambridge, attached 80 electrodes to miniature radio receivers and implanted them into a sightless volunteers brain. Subject reported seeing phosphenes.

1992 a blind volunteer at the U.S. National Institute of Neurological Disorders and Stroke
==> recognized phosphene letters

Two approaches:

• Retinal implants - to avoid brain surgery; requires health optic nerve and nerves to retina
  • MIT and Harvard: 20 micron thick retinal implant - will link to camera in glasses frame via laser diode
  • Duke University
• Cortical implants - requires brain surgery (Utah team uses a 1 cm² hole in the skull)
  • since it penetrates the visual cortex it produces highly localized stimulation
  • can have higher mass than retina implant (since movement is slower than eye movement)
  • Current 10x10 array is 4.2mm x 4.2mm, base of electrode is 80 mm
  • Each electrode is tipped with platinum or gold (or iridium)
  • Each electrode is insulated with polyimide [which has know adhesion when exposed long term to body temperature saline]
  • Currently wire attachments are made to the back side of the array (by ultrasonic welding) - the wires then connect to a percutaneous connector
  • the array is inserted pneumatically in the brain - to provide good electrode depth