Biological Sciences 300/301, Smith College | Neurophysiology
Case 5: How feasible are retinal implants?
A tiny camera mounted on eyeglass frames would send visual images and patterns of electric signals to an antenna and electrode chip sewn to the back wall of the eye. Only the less-than-hair-thin, flexible array at the left end of the device would be implanted in the retina, where nerve cells send signals to the vision center in the back of the brain.
Excerpted from Harvard
University Gazette,
Feb. 19, 2004:
Electric eye under
development
Artificial retina nearly in sight
By William J. Cromie
Harvard News Office
Severely blind people have been able to temporarily see patterns of light with the help of an electric device developed by a Harvard-M.I.T. research team.
Five people with retinitis pigmentosa, the leading cause of inherited blindness, reported seeing spots and lines of light with the help of the device. A sixth person, about to lose her sight to cancer, also saw the light patterns. The retina is a screen of cells at the back of the eye that records light coming through the pupil and converts it to nerve pulses that register as vision at the back of the brain. The artificial retina directly excites these nerve cells with electric probes.
... The research team's overall goal is to improve the quality of life for the 1.6 million people worldwide who have lost their sight to retinitis pigmentosa and the millions more who are afflicted with macular degeneration, a progressive loss of vision with age. Seeing basic light patterns is a first step toward enabling these sightless people to walk safely in unfamiliar places, such as streets, stores, buses, and trains. After that might come enough vision to recognize faces, even to discern emotional expressions. Finally, it may be possible for the blind to read magnified text.
Those working toward such goals foresee a minute camera mounted on eyeglass frames. The visual scenes in its lens would be converted to electrical patterns by a computer microchip, then radioed to an array of wires ten times thinner than a human hair. The wires would send the same signals into the brain as the sight of a smiling face on a sunlit day.
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Cross-section through the
retina GC =ganglion cells |
Question: Does retinal anatomy limit an implant's ability to simulate high-resolution vision in the center of the visual field?