University of New South Wales (UNSW) engineers are examining ways that solar panels can be implanted in the human retina to restore sight.
Dr Udo Roemer, who specialises in solar panel technology, is in the early stages of researching how solar technology can be used to convert light entering the eye into electricity, bypassing the damaged photoreceptors to transmit visual information to the brain.
“People with certain diseases like retinitis pigmentosa and age-related macular degeneration slowly lose their eyesight as photoreceptors at the centre of the eye degenerate,” Roemer said.
“It has long been thought that biomedical implants in the retina could stand in for the damaged photoreceptors. One way to do it is to use electrodes to create voltage pulse that may enable people to see a tiny spot.”
He adds: “There have already been trials with this technology. But the problem with this is they require wires going into the eye, which is a complicated procedure.”
The concept entails a tiny solar panel attached to the eye which converts light into the electric impulse that the brain uses to create visual fields. The panel would be naturally self-powered and portable, without requiring cables and wires into the eye.
Roemer is focusing on semiconductor materials such as gallium arsenide and gallium indium phosphide, as its properties are easier to tune as opposed to silicone-based devices.
“In order to stimulate neurons, you need a higher voltage than what you get from one solar cell,” Roemer said.
“If you imagine photoreceptors being pixels, then we really need three solar cells to create enough voltage to send to the brain. So, we’re looking at how we can stack them, one on top of the other, to achieve this.
“With silicon this would have been difficult, that’s why we swapped to gallium arsenide where it’s much easier.”
Roemer said the technology is in the proof-of-concept stage and is still a way down the track before it will be implantable in the retinas with degenerative eye diseases.
“So far we’ve successfully put two solar cells on top of each other in the lab on a large area – about 1cm2, which has got some good results,” he said.
Roemer said the next step will be to make them into the tiny pixels required for sight and etching the grooves to separate them followed by increasing the stack to three solar cells.
He envisages by the time this technology will be able to be tested in humans – after extensive testing in the lab, and testing in animal models – the device will be approximately 2mm2 in size with pixels measuring about 50 micrometres (five hundredths of a millimetre).
“One thing to note is that even with the efficiencies of stacked solar cells, sunlight alone may not be strong enough to work with these solar cells implanted in the retina,” he said.
“People may have to wear some sort of goggles or smart glasses that work in tandem with the solar cells that are able to amplify the sun signal into the required intensity needed to reliably stimulate neurons in the eye.”
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