Expert Comments
Richard Normann, Ph.D., University of Utah:
“The results of W. H. Dobelle’s description in the lay press are encouraging for the field of artificial vision. The demonstration that surface electrodes can be implanted for over two decades and retain the ability to stimulate cortex is encouraging. But many more years of basic research is needed before systems like this, cortical or retinal, could provide restoration of useful vision to blind patients.”
Mark Humayun, M.D., Ph.D., Wilmer Ophthalmological Institute:
“Positives about this work are that 1) the electrodes implanted over the visual cortex survived and remained functional; and 2) that the visual cortical neurons remained healthy enough to respond to electrical stimulation over many decades. However, there are also remaining questions and concerns: 1) most investigators in this field believe that more electrodes to generate more phosphenes are needed to result in useful vision, and 2) in order to increase the number of electrodes and phosphenes, electrodes need to penetrate into the visual cortex and not just reside on the cortical surface. This positioning of intracortical electrodes has been associated with fibrosis around the tip of the electrode as well as carries the risk of intracortical bleeding during insertion.”
Future Research
The Dobelle Institute, Inc. plans further testing of this technology, using larger electrode arrays, more powerful computers and more sophisticated image processing. The Dobelle artificial vision system is not commercially available in the United States. Additional basic research to prove the concept and clinical trials to demonstrate safety and effectiveness will probably take several years and is critical for developing a base of scientific evidence in order to make decisions regarding clinical application.
*This information is designed to inform ophthalmologists and their patients of current clinical developments in a summary fashion, and does not reflect a position or policy of the American Academy of Ophthalmology or its Board of Trustees. This information is time-limited, and based solely on a summary review of articles available as of January 2000. The material provided is informational only, and is not intended to be a basis for diagnosis, treatment or any other clinical application.
References
Foerster O: Beitrage zur Pathophysiologie der Sehbahn und der Sehshpare. J. Psychol. Neurol. , Lpz, 1929; 39:463-85.
Dobelle WH and Mladejovsky WG: Phosphenes produced by electrical stimulation of human occipital cortex and their application to the development of a prosthesis for the blind. J. Physiol. 1974; 243: 553-76.
Schmidt EM, Bak et al: Feasibility of a visual prosthesis for the blind based on intracortical microstimulation of the visual cortex. Brain 1996; 119:507-22.
Rousche PJ and Norman RA: Chronic intracortical microstimulation (ICMS) of cat sensory cortex using the Utah Intracortical Electrode Array. IEEE Trans Rehab Eng 1999; 7:56-68.
Dobelle WH: Artificial vision for the blind by connecting a television camera to the visual cortex. ASAIO Journal 2000; 46:1-7.
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