Artificial retina keeps cool by knowing what to ignore
Artificial retinas have the potential to restore some sight to people with certain kinds of blindness, but they have their own problems. For one, complex electronics often overheat, which is bad enough in a phone or laptop but definitely not something you want in your eyeballs. Now a Stanford team has found a way to potentially bypass the issue by being more selective about what data is processed.
An artificial retina is essentially a camera sensor implanted onto the back of the inner eye, which collects light entering the eye and translates it into electrical signals. These signals are passed through an array of electrodes on the other side and into neurons that then relay the data via the optic nerve to the brain, where it can process what it’s seeing.
At least, that’s how it should work – in reality the technology isn’t quite there yet. With hundreds of electrodes generating electrical impulses, a huge amount of heat is created at the same time, which would basically fry the tissue at the back of the eye. Obviously, that’s not ideal.
So the Stanford team set out to find a way to reduce that heat. The simplest way to do so is to cut back on the amount of data that’s being crunched right there in the eye. Ideally that would be done without lowering the amount of visual information being extracted.
The team says that the visual information has to be digitized, and then compressed to get it to communicate with the neurons at the back of the eye. In previous versions these were two separate steps, but now the researchers have combined them to reduce the amount of data that needs to be stored and transferred.
The natural retina is made up of different cells that react to light differently, and the researchers are able to tell what type of cell created a particular electrical signal by the shape of its “wave.” From there, the team learned that they can ignore certain types of signals. If a single electrode registers a signal, then the artificial retina knows it’s important and will store and process it. But if several electrodes register the same signal, then it’s considered noise and can be ignored.
Using this process, the artificial retina is able to work far more efficiently without affecting the amount of visual information that passes through. In tests, the team cut the amount of data acquired by a factor of 40, while only missing five percent of cells.
Currently, these artificial retinas only use a few hundred electrodes, but a high-resolution digital retina would need tens of thousands of them. Heat would be even more of a problem in that case, so the researchers say that this is an important step towards that goal.
The research was published in the journal IEEE Transactions on Biomedical Circuits and Systems.