A US biomedical engineering team has announced the development of an artificial vision system for a totally blind person,with an ability to deliver a visual acuity of about 20/400.
The system uses a sub-miniature television camera and an ultrasonic distance sensor, both of which are mounted on a pair of eyeglasses. The sensors connect through a cable to a miniature computer which is worn on a belt. After processing the video and distance signals, the computer uses sophisticated computer-imaging technology, including edge-detection algorithms to simplify the image.The computer then triggers a second microcomputer that transmits pulses to an array of 68 platinum electrodes implanted on the surface of the brain's visual cortex.
Bringing wires through the skin without discomfort or infection is one of many independent inventions that has made the new visual prosthesis possible.When stimulated, each electrode produces one to four closely spaced phosphenes, which have been described as resembling 'stars in the sky'. These white phosphenes appear on a black background 'map' which is roughly 20 cms by 5 cms at arms length.
After six generations of improvement over the last 21 years, the external electronics package has now been miniaturized so it is about the size of a dictionary and weighs approximately 4.5 kilos, including batteries.
Dr. Dobelle said that the new artificial vision systems are expected to be made available, on a limited commercial basis, starting later this year.
