Transforming nerve cells into light-sensing cells aims to restore sight in some blind patients
Eye: Tony Graham/Getty Images, adapted by J. Hirshfeld; webvision.med.utah.edu, adapted by J. Hirshfeld
A man who had been blind for 50 years allowed scientists to insert a tiny electrical probe into his eye.
The man’s eyesight had been destroyed and the photoreceptors, or light-gathering cells, at the back of his eye no longer worked. Those cells, known as rods and cones, are the basis of human vision. Without them, the world becomes gray and formless, though not completely black. The probe aimed for a different set of cells in the retina, the ganglion cells, which, along with the nearby bipolar cells, ferry visual information from the rods and cones to the brain.
No one knew whether those information-relaying cells still functioned when the rods and cones were out of service. As the scientists sent pulses of electricity to the ganglion cells, the man described seeing a small, faint candle flickering in the distance. That dim beacon was a sign that the ganglion cells could still send messages to the brain for translation into images.
That 1990s experiment and