An Artificial Retina Implant Could Be The Solution To Retinal Degeneration

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Mar 13, 2017
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I must say, rats are subject to so many tests that I am beginning to feel sorry for them even though they scare me a little. Once again, scientists have tested on these poor creatures and have developed something new in the field of medicine. This time they have come up with a retinal implant in rats that can restore lost vision. The researchers plan on taking this procedure to the next level by conducting trials for humans later in the year.

Rats, Retina and Researchers

The implant helps convert light into electrical signals that in turn stimulate the retinal neurons. This implant gives hope to all those who undergo retinal degeneration including retinitis pigmentosa – breakdown of photoreceptor cells in the eye that results in blindness. Millions of these photoreceptor cells make up the retina that is located at the back of the eye. If a mutation takes place in any of the 240 identified genes, retinal degeneration takes place and the cells die off. Retina is affected even if the nerves around it aren’t affected.

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Since the nerves work fine, previous research has tried dealing with retinitis pigmentosa by using bionic eye devices that stimulate the surrounding neurons using light. Some researchers have also tried using CRISPR gene editing for repairing mutations that lead to blindness. A research team led by the Italian Institute of Technology has come up with a new approach to solve this problem. It involves using a prosthesis implanted into the eye and this serves as a replacement for the damaged retina.

The implant consists of a thin conductive polymer placed on silk-based substrate and covered with a semiconducting polymer. This semiconducting polymer acts as a photovoltaic material and absorbs light as it enters the eye. Once the light enters, the retinal neurons are stimulated and fill the gap that has been left by the damaged cells. The device was tested by being placed in the eyes of rats that had been bred to develop a rodent model of retinal degeneration – Royal College of Surgeons (RCS) rats.

RCS rats and future of research

Once the rats healed from the operation (30 days later), it was tested how sensitive the RCS rats were to light compared to healthy rats. This sensitivity check is known as the papillary reflex. It was observed that at an intensity of 1 lux, which is a bit brighter than the light from a full moon, the RCS rats had almost similar sensitivity to the healthy rats. When the intensity was increased to 4-5 lux, the sensitivity response was largely indistinguishable. When the same tests were conducted 10 months after the surgery had taken place, the implants were still effective but there had been minor vision impairments in all the rats due to age.

PET (position emission tomography) was used to monitor the brain activity during the sensitivity tests and it was observed that the primary visual cortex showed an increase in activity. The team concluded that the implants directly activated, “residual neuronal circuitries in the degenerate retina” but further research is still necessary to understand how the stimulation works. It was said in the paper, “[T]he detailed principle of operation of the prosthesis remains uncertain.”

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Even though there are no guarantee whether the research will be successful in rats entirely, the team is very hopeful that it will be successful and they will be able to do human trials soon enough. According to one of the team member, ophthalmologist Grazia Pertile from the Sacred Heart Don Calabria in Negrar, Italy, “We hope to replicate in humans th. e excellent results obtained in animal models. We plan to carry out the first human trials in the second half of this year and gather preliminary results during 2018. This [implant] could be a turning point in the treatment of extremely debilitating retinal diseases.”

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