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
learned to 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
