The European Dreams Project team is currently developing a new generation of retinal prostheses that haven’t been tested on humans yet. But an experiment conducted with an American prosthesis that was implanted in 30 subjects proves the procedure works. When the chip is implanted in the eyes of patients who’ve lost their sight, it restores a simplified form of vision. Unfortunately, those who were born blind aren’t able to benefit from this innovation. The sole drawback: with just 60 pixels to compose the image, only shapes and colors can be recognized. A resolution that the nanodiamond being developed by the Dreams Project will increase to 1,000 pixels, finally enabling patients to get around on their own.
Dr. Philippe Bergonzo, CEA-LIST Saclay, France, is Project coordinator of the European Commission-funded project Dreams, working on new types of nanotransducers, electric devices converting energy from one form to another, based on artificial nanocystalline diamond.
How do the nanotransducers you are developing within the Dreams project work on the retina?
The retina is a two-dimensional screen. We stimulate the image at the back of the eye and this image is sent to the brain using all the natural steps of the vision process, i.e., recovering an electrical signal and sending it to the brain. We need a material that’s biocompatible. Here at the Dreams project, we’re working on the diamond which is a carbon material. It’s based on carbon which is very abundant on earth – in coal and in methane. We take methane – in the form of municipal gas – and use it to make a synthetic diamond. This diamond is directly used as a semiconductor. It’s a material that’s electrically conductive but not too much and it can directly stimulate the cells of the retina.
How are these synthetic diamonds produced?
The diamond used to coat the implants isn’t a precious stone, but a synthetic material produced in a machine. Methane gas is heated to 800 degrees to eliminate the hydrogen and is then transformed into a carbon deposit. In other words, diamond. This procedure allows us to make a diamond that can be even purer than a natural diamond. But it’s actually an assembly of tiny nanometric diamond crystals stuck together to form a whole, a continuous diamond film.
How can deteriorated photoreceptors be activated through nanodiamond-coated retinal protheses?
This project is intended for patients who have gone blind, who have lost their photoreceptors. There are several layers of neurons in the retina, and when the photoreceptors deteriorate, there are only two layers of neurons left. The idea of the retinal prosthesis is to electrically stimulate these layers of neurons so they can send visual information to the brain.
Which is the optical resolution you have achieved to date?
The concept has been proven. It is possible to to compose images made of 60 pixels – since there are 60 electrodes. The resolution isn’t very good. The objective is to increase the number of pixels, to try and move on to a prosthesis that would already have 1000 pixels and that would theoretically allow patients to read and maybe even get around on their own. What we’ve done is show that we can indeed use diamonds and that neurons are going to develop in contact with these diamonds.