A promising new study suggests that a wireless, light-sensitive, and flexible film could potentially form part of a prosthetic device to replace damaged or defective retinas. The film both absorbs light and stimulates neurons without being connected to any wires or external power sources, standing it apart from silicon-based devices used for the same purpose. It has so far been tested only on light-insensitive retinas from embryonic chicks, but the researchers hope to see the pioneering work soon reach real-world human application.
Some neurons are genetically-predisposed to be sensitive to light. An emerging field called optogenetics uses light to stimulate and control those neurons, with applications not only in vision but also in gene therapy, brain mapping, reducing pain sensitivity, treatment of neurological disorders such as epilepsy and Parkinson's disease, and even mind control.
The researchers sought to develop an optogenetics approach to restoring vision. They combined semiconductor nanorods and carbon nanotube film and found that the resultant system stimulated neurons in light-insensitive embryonic chicks at day 14 of their development when illuminated with violet light for 100 ms.
Most previously-tested artificial vision technologies are silicon based, with rigid, non-transparent photoconductive chips implanted (often invasively and with great complexity) into the subject and connected to an external power source. These older systems also suffer from long-term stability issues and low spatial resolution, the researchers note.
"We hope our carbon nanotube and semiconductor nanorod film will serve as a compact replacement for damaged retinas," said lead researcher Yael Hanein. His colleague Lilach Bareket cautions, however, that scientists are "still far away from actually replacing the damaged retina."
If the technology does prove viable for use in humans, we could see it applied in treatment of age-related macular degeneration, which currently affects as many as 15 million Americans, and in other retina-based vision problems – including many forms of blindness.
The research was conducted by an international team spread across Tel Aviv University, the Hebrew University of Jerusalem, and Newcastle University. A paper describing the work has been published in the journal Nano Letters.