An ocular implant that incorporates solar panels into the human retina that researchers at the University of New South Wales (UNSW) in Australia are working on could restore vision in people who have damaged retinal photoreceptor cells due to diseases such as retinitis pigmentosa and age-related macular degeneration (AMD)
Neuroprosthetics is a technology that uses devices designed to interact with the nervous system and restore lost functions and is a developing field that promises to significantly improve quality of life. A well-known example of these devices is the cochlear implant, which converts sounds into electrical signals by directly stimulating the auditory nerve in people with severe hearing loss.
Now, the question is whether something similar could be done for the human eye and restore vision in people with damaged photoreceptors, the cells responsible for detecting light and color. A multidisciplinary group of researchers from around the world – including engineers, neuroscientists, clinicians and other biotechnology experts – believe it is possible, although small steps are being taken for now.
Dr Udo Roemer, a UNSW researcher and specialist in photovoltaics, commonly known as solar panel technology, is in the early stages of research into how solar technology can convert light entering the eye into electricity. This would allow visual information to be transmitted to the brain, bypassing damaged photoreceptors. “People with diseases such as retinitis pigmentosa or age-related macular degeneration (AMD) gradually lose their sight as the photoreceptors in the center of the eye degenerate,” says Dr. Roemer.
Send signals to the brain so it can create visual fields
It has long been considered that biomedical implants in the retina could replace damaged photoreceptors. One way to do this would be through electrodes that generate voltage pulses that could allow people to see small dots. Tests have already been carried out with this technology, but they require cables inside the eye, a complex procedure, says Roemer. An alternative would be to have a small solar panel attached to the eyeball that converts light into the electrical impulse that the brain uses to create our visual fields. This panel would be self-contained and portable, eliminating the need for cables.
Dr. Roemer is not the first to investigate the use of solar cells to help restore sight. However, instead of focusing on silicon-based devices, he has turned his attention to other semiconductor materials such as gallium arsenide and gallium indium phosphide, mainly because it is easier to tune the properties of these materials. They are also used in the solar industry to make more efficient solar panels, although they are not as economical as general-purpose silicon.
“People may need to wear some type of smart glasses that can amplify the sun’s signal to the intensity needed to reliably stimulate the neurons in the eye.”
“To stimulate neurons, you need a higher voltage than a single solar cell can provide,” explains Dr. Roemer. “If we imagine the photoreceptors as pixels, then we really need three solar cells to create enough voltage to send to the brain. “That’s why we’re looking into how we can stack them, one on top of the other, to achieve this.” “With silicon this would have been difficult, so we switched to gallium arsenide where it is much easier,” he adds.
Dr. Roemer has highlighted that the research is in the proof-of-concept stage. “So far we have managed to place two solar cells on top of each other in the laboratory in a large area, about 1 cm2, and we have obtained good results,” he says.
The next step will be to reduce these cells to the small pixels necessary for vision and record the grooves to separate them. Afterwards, it will be a small step to increase the stack to three solar cells. Dr. Roemer predicts that by the time this technology is ready to be tested in humans, after extensive laboratory testing followed by testing in animal models, the device will be approximately 2 mm2 in size with pixels of about 50 micrometers.
However, he notes that even with the efficiency of stacked solar cells, sunlight alone may not be enough to power these retinal-implanted solar cells. “People may need to wear some type of protective glasses or smart glasses that work in conjunction with solar cells and can amplify the solar signal to the intensity needed to reliably stimulate neurons in the eye,” he concludes. .
