Researchers in Sweden and Israel are collaborating to design a simple retinal prosthetic device that could help restore sight to people with certain types of blindness. A chunk of the photoactive film is similar to a pixel in a digital camera sensor, and can convert light impulses to electrical signals to stimulate nerve cells in the eye. While the implant is at an early stage of testing, the researchers hope that one day it could help blind people to see again.
Certain types of visual impairments arise because light-sensitive cells in the retina have been damaged or degraded, meaning that they no longer convert light into electrical pulses that activate the optic nerve. For affected people, a retinal implant that can replace the lost light-sensitive cells could mean vision restoration.
This is the goal of these researchers, who have developed a retinal implant using widely available and inexpensive organic pigments. The pigments are non-toxic and are frequently used in cosmetics and within printing and tattooing inks. The researchers describe the implant as having a doughnut shape, with semi-conducting pigment nanocrystals in the center, and a surrounding metal ring.
The implant does not require external connections, and there is no delay between a light signal activating the implant and direct stimulation of nerve cells. “The response time must be short if we are to gain control of the stimulation of nerve cells,” said David Rand, a researcher involved in the study. “Here, the nerve cells are activated directly.”
So far, the researchers have tested the device in the lab, and found that it could stimulate light-insensitive retinas. However, further tests are required before the implant can be trialed in humans.
“We have optimized the photoactive film for near-infrared light, since biological tissues, such as bone, blood and skin, are most transparent at these wavelengths,” said Eric Glowacki, a researcher involved in the study. “This raises the possibility of other applications in humans in the future.”
Study in Advanced Materials: Direct Electrical Neurostimulation with Organic Pigment Photocapacitors…