Retinal Prosthesis Allows Blind Patient to "Read"
Patient correctly identifies most letters, many words with direct stimulation of the retina
THURSDAY, Nov. 29 (HealthDay News) -- For patients with retinal prostheses, text can be successfully stimulated to electrodes in the prosthesis system and read as visual Braille, according to a study published online Nov. 22 in the Frontiers in Neuroprosthetics.
Thomas Z. Lauritzen, Ph.D., from Second Sight Medical Products in Sylmar, Calif., and colleagues examined the option of using an epiretinal prosthesis, the Argus II retinal prosthesis system, to stimulate visual Braille as a sensory substitution for reading written letters and words. The retinal prosthesis system includes an epiretinally-implanted electrode array, a video camera mounted on a pair of glasses, and a wearable computer that processes the video and stimulates the electrodes in real time. Groups of electrodes were stimulated directly, bypassing the camera, to create visual perceptions of Braille letters. An alternative forced choice paradigm was used to stimulate single letters and an open-choice reading paradigm was used to stimulate short words. All experiments were performed on a single subject.
The researchers found that the individual correctly identified 89 percent of single letters. The individual correctly identified 80, 60, and 70 percent of two-, three-, and four-letter words, respectively.
"There was no input except the electrode stimulation and the patient recognized the braille letters easily," Lauritzen said in statement. "This proves that the patient has good spatial resolution because he could easily distinguish between signals on different, individual electrodes."
Several authors are employees of and have financial interests in Second Sight Medical Products, manufacturers of the Argus II.