The Artificial Vision Endgame

Scientists have long dreamed of restoring sight to the blind.  But so far, the only approach that has brought the blind some semblance of sight is the implantation of retinal prostheses – arrays of tiny electrodes that fire in response to input from a camera. They’re a revelation to those who have received them – but recipients are not going to be driving down to the shops any time soon...

Close your eyes and rub them hard. If you see little spots of light, those are phosphenes – and this is what the electrodes evoke when activated by the camera. It’s nothing like normal vision, but it’s enough to tell the difference between light and dark, or a wall and doorway, and it helps the blind recover some of their independence. Unfortunately, the implants don’t work for everyone – they only replace the function of the light-sensing photoreceptors and rely on the rest of the retina to be sufficiently intact to relay the signal to the optic nerve and on to the brain. If the patient has a retina ravaged by wet age-related macular degeneration or an optic nerve destroyed by glaucoma, no “bionic eye” could ever help. But there is another approach: visual cortex prostheses (VCPs). First envisaged back in the 1920s (1), VCPs bypass the eye completely and stimulate the part of the brain that’s ultimately responsible for processing most of your vision: the visual cortex.

Nearly 100 years later, Second Sight recently reported the “first successful implantation and activation of a wireless multichannel visual cortical stimulator in a human subject,” providing proof of concept for the company’s Orion I visual cortical prosthesis. There are good reasons why it has taken almost a century to get VCPs to this stage; placing the implant requires craniotomy, and once you’ve removed a portion of the skull to gain access to the brain, you have to deal with a brain anatomy that’s both distorted relative to the visual input, and plastic to neural input. In other words, even if you can safely place it, can you “tune” it and keep it tuned over time without requiring repositioning? There are also worries over “kindling” – seizures caused by electrical stimulation. However, for the millions of people worldwide who are legally blind, the impact could be huge.

“We expect patients to find objects, follow lines, conduct orientation and mobility,” says Second Sight’s Vice President, Gregoire Cosendai, but adds that it is too early to tell if those hopes will be realized.

The company reported that the first patient to receive the Orion I device “was able to perceive and localize individual phosphenes with no significant adverse side effects” – much like a patient with a retinal prosthesis.