The advent of cochlear implants in the 1970s and ocular implants in the early 2000s revolutionised hearing and vision loss treatment by circumventing damaged organs with digital prostheses that directly stimulated neural pathways. But these devices have been poor substitutes for the real thing. That is, until now.
For those of us with functioning vision, the rods and cones within the eye translate incoming light into electrical pulses feeds them through the retina into the brain where the signals are recombined into the images we see. However, people suffering from hereditary eye diseases like retinitis pigmentosa, the rods and cones fail. The rest of the neural pathway from the retina on back still work just fine but are generally useless without the photoreceptors generating the initial electrical impulses.
Much like cochlear implants before it, the Argus II artificial retina sidesteps these damaged photoreceptors and injects visual information directly into the optic nerve. First introduced by pioneering American prosthetics firm, Second Sight, in 2002, the Argus II employs a three-part system. A glasses-mounted miniature camera captures images of the environment around its wearer then transmits these images to an attached Video Processing Unit (VPU) which translates the image into coding instructions. These instructions are then sent back to the glasses which transmit them wirelessly to the implanted artificial retina. The ocular implant consists of an 60-block electrode array that emits electrical pulses to activate different strands of the optic nerve and generate a perceptible pattern of light for the user. With this system, people could “see” movement, colour, and the outline of objects around them but the electronic eye was never acute enough for reading so patients remained reliant on finger-read Braille. But no longer.
A small Swiss study published in the journal Frontiers demonstrates that the Argus II can also be modified to transmit Braille patterns across just six of the system’s 60 electrodes directly into a patient’s brain, allowing him to quickly and accurately recognise short words — essentially allowing him to read without relying on the system’s camera.
“In this clinical test with a single blind patient, we bypassed the camera that is the usual input for the implant and directly stimulated the retina. Instead of feeling the braille on the tips of his fingers, the patient could see the patterns we projected and then read individual letters in less than a second with up to 89 per cent accuracy,” Lead author and researcher Thomas Lauritzen said in a press release. “There was no input except the electrode stimulation and the patient recognised the braille letters easily. This proves that the patient has good spatial resolution because he could easily distinguish between signals on different, individual electrodes.”
While the Argus II is still a bleeding-edge technology — only about 50 people worldwide have had the $US100,000 device installed — researchers continue to find new and innovative uses for the technology, bringing it closer and closer to the mainstream. [Frontiers – PopSci – 2nd Sight – HuffPo – Wikipedia]
Image: AP Photo/Martin Cleaver