No abstract

Blindness is more feared by the public than any ailment with the exception of cancer and AIDS. We report the development of the first visual prosthesis providing useful "artificial vision" to a blind volunteer by connecting a digital video camera, computer, and associated electronics to the visual cortex of his brain. This device has been the objective of a development effort begun by our group in 1968 and represents realization of the prediction of an artificial vision system made by Benjamin Franklin in his report on the "kite and key" experiment, with which he discovered electricity in 1751.

✓ The topographical anatomy of the primary visual cortex in man was studied by macroscopic identification and measurement of the line of Gennari on coronal sections from 52 hemispheres collected at autopsy. Computer analysis of these data provided detailed, quantitative information concerning the amount, variability, and distribution of the striate area on the surface of the occipital lobe, and within the calcarine fissure and other sulci. This information is particularly applicable to the development of a functional visual prosthesis for the blind based on stimulation of the visual cortex. Taking conservative values for two-point discrimination (3 mm) on the cortex based on previous observations made during neurosurgical operations, and the surgically accessible areas available for stimulation reported in this study, it seems clear that a useful number of electrodes could be implanted in virtually every patient.

Electrical stimulation of the occipital cortex resulted in discrete photic sensations or "phosphenes" in two volunteers who had been totally blind for 7 and 28 years, respectively. Stimulation of multiple electrodes allowed one patient to recognize simple patterns, including letters. Both patients made an uneventful recovery, and the success of these experiments reinforces the hope that a functional visual prosthesis can be developed, although many problems remain to be solved.