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Friday, November 23, 2012
New Device Stimulates Retina So Blind People Can Read
Researchers have streamed braille patterns directly into a blind person’s retina for the first time, offering the ability to read four-letter words accurately and quickly.
The ocular neuroprosthetic device, the Argus II, has been implanted in over 50 patients, giving them the ability to see color, movement and objects.
The device uses a small camera mounted on a pair of glasses, a portable processor to translate the signal from the camera into electrical simulation, and a microchip with electrodes implanted directly on the retina.
“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% accuracy,” researcher Thomas Lauritzen, lead author of the paper, said in a statement.
The visual implant uses a grid of 60 electrodes to stimulate patterns directly onto the nerve cells. During the study, Second Sight researchers used a computer to stimulate six of those points on the grid to project the braille letters.
They conducted a series of tests with single letters as well as words ranging in length from two letters up to four. The patient was shown each letter for half a second, and had up to 80 percent accuracy for short words.
“There was no input except the electrode stimulation and the patient recognized the braille letters easily. This proves that the patient has good spatial resolution because he could easily distinguish between signals on different, individual electrodes.” Lauritzen said.
Silvestro Micera at EPFL’s Center for Neuroprosthetics said the study is a proof of concept that points to the importance of clinical experiments involving new neuroprosthetic devices to help improve this technology.
The implant is primarily for those who suffer from the genetic disease Retinitis Pigmentosa (RP). It has been shown to restore limited reading capability of large conventional letters and short words when used with the camera.
While reading should improve the future interactions of the Argus II, the current study shows how the device could be adapted to provide an alternative and potentially faster method of text reading.
Performing image processing in software prior to sending the signal to the implant is a unique trait in the Argus II device.