Seeing is believing in nanotechnology

Israeli scientists, together with researchers in the UK, are working on perfecting a technique that could one day form the basis of a prosthetic retina to help people suffering from eye damage or degeneration.

Using nanotechnology, the light-sensitive film, composed of nerve cells, converts images to electrical impulses and sends them to the brain, where they get converted back into images — shapes and shadows, at minimum — that are then transmitted to the optic nerve, which then “sees” what the eye is looking at.

“It’s like seeing from the inside what you can’t see from the outside,” said Nir Waiskopf, a Hebrew University graduate student working with research leader Professor Uri Banin on the project.

The research was published in the industry publication Nano Letters.

What is special about the technology, developed by the Hebrew University scientists with colleagues from Tel Aviv University and Newcastle University in the UK, is that the input mechanism – the device that lets blind users “see” – goes into the eye itself.

“Our system is the first one that doesn’t require external equipment,”  Wasikopf said. “The film is implanted in the eye, and using nanotechnology it processes what the eye is looking at and converts it into an image that is sent to the optic nerve.”

The most advanced of the currently available artificial vision systems is the Argus II Retinal Prosthesis System, approved by the US Food and Drug Administration. This system restores some functional vision for people suffering from blindness, according to its maker, Second Sight Systems.

While the principles of how the Argus works are similar to the ones used by the one being developed by Hebrew University, the process of how the images get into the brain and to the optical nerve is different.

The Hebrew university-developed system combines semiconductor nanorods and carbon nanotubes to create a wireless, light-sensitive, flexible implantable film. The film transforms visual cues to electric signals, mimicking the function of the photo-sensitive cells in the retina. Essentially, the film is a stand-in for the retina, taking over its functions and operating in the same manner that a working retina would, with the imaging processing done on the film using nanotechnology.

It looks good on paper, and so far, the animal experiments conducted by the team have been successful, according to Waiskopf, but much work remains until this can provide a practical solution, he stressed.

“We have a lot of hurdles to jump, starting with testing in humans, and it could be a long time – maybe five years or more – before we get FDA approval for this. But I’m hopeful that we will be able to cut that timeframe down.”

The experiments so far have concentrated on providing images that indicate shape and size, and light and darkness. Like with the Argus system, the university-developed film does not restore sight artificially in the way people who can see understand it – at least not yet.

“Because we are experimenting on animals who cannot tell us what they are seeing, we can’t really be sure how well it is working,” Wasikopf said.

That it is working at all is indicated by the reactions of animals, who respond to light when outfitted with the film, when they previously were unable to. “But we won’t really get answers about resolution and depth until we try it out on people,” he said.

Wasikopf, however, is optimistic about the prospects for the system.

“Because we are using nanotechnology to accomplish this, we will be able to use different nanoparticles on the film in order to stimulate different responses. For example, we could use nanoparticles that are sensitive to different colors and have a mechanism to ‘mix’ the colors, allowing the user to ‘see’ in color,” which no system currently available is capable of,” he explained.

The team’s research shows that the system already provides more light sensitivity than camera-based systems. “We are constantly optimizing it, so we expect results to continue to improve,” Wasikopf added.

According to the researchers, the new device is compact, capable of higher resolution than previous designs, and is also more effective at stimulating neurons. While much work remains, researchers hope their carbon nanotube-semiconductor nanocrystals film will one day effectively replace damaged retinas in humans.

“This is pioneering work,” said Prof. Banin. “We hope this can lead to future implementation of this approach in retinal implants.”