Paris - A French person who is completely blind due to retinitis pigmentosa can decipher Braille with the help of retinal prosthesis. According to report in Frontiers in Neuroprosthetics (2012; doi: 10.3389 / fnins.2012.00168) the patient can recognize short words relatively “fluently”.
“Argus II” is one of series of retinal prostheses that to enable blind people to see minimally. The model from the manufacturer Second Sight from Sylmar near Los Angeles is placed on the retina in surgical procedure. It contains 60 small electrodes that deliver individually controlled electrical impulses to the retina, which are then passed on to the visual cortex via the optic nerves. "Argus II" receives the signals wirelessly from control unit. It reduces the recording of video camera attached to the glasses to resolution of 60 pixels.
Braille needs only 6 pixels. They correspond to the individual points with which the letters and individual symbols are coded. Usually they are felt with the fingers. The dots in Braille were now sent to the retina as electrical signals for the patient who was not named. After little practice, he was able to name 89 percent of the letters correctly.
80 percent of words made up of two letters, 60 percent of words made up of three letters and 70 percent of words made up of four letters were recognized, reports Thomas Lauritzen from the manufacturer Second Sight. That should not be enough to read texts fluently. However, the manufacturers are confident that the results can still be improved, especially since most of the errors were caused by the misinterpretation of individual points.
In the long term, the retinal prosthesis could become an alternative to current reading devices, Lauritzen hopes. Ideally, the patient would use scanner to load the texts into the control unit, which forwards them to the retina prosthesis as Braille signals.
The subretinal retinal implants from the manufacturer Retina Implant from Reutlingen also make this possible Patients recognize individual letters. The German working group insists that the patients master the more demanding task and can decipher block letters.