Benjamin Franklin as inspiring source for ingenious system to guide blind people through the subway

New York 18 January 2000A biomedical engineering team has designed an artificial vision system providing independent mobility to blind people. The system, reflecting more than thirty years in development work by the Dobelle Institute in New York City and its affiliates on Long Island and in Switzerland, allows a totally blind person to achieve visual acuity of about 20/400 within a narrow visual "tunnel". The new device at last materialises Benjamin Franklin's prediction of an artificial vision system he wrote down in his report on the "kite and key" experiment, with which he discovered electricity in 1751.

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The "Dobelle Eye", as described in the latest issue of The Journal of American Society of Artificial Internal Organs (ASAIO), and in companion commentaries in Nature and Lancet, consists of a sub-miniature television camera and an ultrasonic distance sensor, which both have been mounted on a pair of eyeglasses. The sensors connect through a cable to a miniature computer, which is worn in a pack on a person's belt. After the video and distance signals have been processed, the computer makes use of sophisticated computer-imaging technology, such as complex edge-detection algorithms, to simplify the image eliminating "noise".

The computer then triggers a second microcomputer which transmits pulses to an array of 68 platinum electrodes implanted on the surface of the brain's visual cortex. The fact that a group of blind volunteers could be implanted with these permanent electrode arrays, which they were able to retain for over two decades without any discomfort or infection, is one of many independent inventions that has made the new visual prosthesis possible. When it is stimulated, each electrode produces one to four closely spaced phosphenes, which have been described as resembling "stars in the sky". This white phosphene on a black background "map" is roughly eight inches by two inches at arms length.

The patient in the official study as it is reported in the ASAIO Journal, is a 62-year-old male who was totally blinded by trauma when he was 36 years old. After learning to use the system and "interpret" the display in a very short time, the patient is now able to read two inch tall letters at a distance of five feet, representing a visual acuity of about 20/400. Although the relatively small electrode array produces tunnel vision, the patient is also able to navigate in unfamiliar environments, like the New York City subway system. When the sub-miniature television camera is replaced with a special electronic interface, this blind man can equally learn to "watch" television, use a computer, and gain access to the Internet.

The computer package employed in the initial system was the size of a large bookcase and weighed several thousand pounds. However, in six generations of improvement over the last 21 years, the external electronics package has currently been miniaturised to about the size of a dictionary and now weighs approximately ten pounds, including batteries. The sub-notebook computer incorporates a 233 MHz microprocessor with 32 Mb of RAM and a 4 Gb hard drive. It also has an LCD screen and keyboard. It was selected because of its very small size and light weight. The belt pack also contains a second micro-controller, and associated electronics to stimulate the brain.

Dr. Dobelle's first human experiments in this artificial vision project started in 1970 and involved cortical stimulation of 37 sighted volunteers who were submitted to surgery on the occipital lobe under local anaesthesia to remove tumours and other lesions. In a following phase, three blind volunteers were temporarily implanted with electrode arrays to stimulate their visual cortex. Subsequent experiments involved four blind volunteers who were implanted with permanent electrode arrays. Percutaneous connecting pedestals were employed in these interventions.

At the Columbia-Presbyterian Medical Center in New York City, the Dobelle system's electrodes and connecting pedestal were surgically implanted in two blind volunteer's brains in 1978. Both have retained their implants and one of them is the person who has become the subject of the study, reported in the ASAIO Journal. Dr. Dobelle stated that the new artificial vision systems are expected to be made available, on a limited commercial basis, starting in the course of this year.

The Dobelle Institute and its commercial affiliates in Long Island, New York, and Zurich, Switzerland, constitute one of the world's highly sophisticated organisations for education, research and development, manufacturing, and clinical implementation of medical devices. Over the last thirty years, the Dobelle Institute has been responsible for the design, manufacture, and the distribution of other neurological "pacemakers" that can control breathing, intractable pain, and also the urogenital system of about 15.000 patients in more than 40 countries. These clinical systems have gained full regulatory and reimbursement approval from the United States Food and Drug Administration, Medicare and analogous foreign agencies.


Leslie Versweyveld

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