Here's a scientific innovation just published by the journal Nature Materials which, if confirmed, would be a blessing for millions of people suffering from blindness or severe visual impairment. Italian researchers have developed a retinal implant that converts light into an electrical signal that stimulates retinal neurons. Experiments are currently being carried out successfully on rats, but scientists expect to move on to human experimentation later this year.
C’is a real hope for millions of people suffering from retinal degeneration, or even retinitis pigmentosa, a condition in which cells break down, leading the patient inevitably to blindness. In this type of pathology caused by the mutation of a gene, while the photoreceptor cells are affected, the retinal nerves remain intact and functional.
Doctors have been working on this for a long time. Experiments have been conducted using bionic eye devices that stimulate neurons with lights. Other experiments are trying to use the famous genetic editing tool CRISPR-Cas9 to repair the mutations that cause blindness.
The innovation brought by the team of doctors at the Italian Institute of Technology is based on a totally biocompatible prosthesis implanted in the eye, whose job will be to take over the deficient retina. The implant is made from a thin layer of conductive polymer placed in a silk substrate coated with a semiconducting polymer. This acts like a photovoltaic material: it absorbs photons when light enters the eye's lens. At this point, the electricity stimulates the retinal neurons as the eye's natural photoreceptors would do if they were undamaged.
Scientists have tested this device by placing implants in rats. Thirty days after the operation, light sensitivity measurements, including pupillary reflex testing, showed that the operation was a success. Indeed, the treated rats were stimulated by a light of 4 to 5 lux, which is equivalent to a twilight sky. Below that, at 1 lux (equivalent to a moonlit night), the rats did not react to light. But above 5 lux, their behaviour is the same as that of healthy rats.
Further tests were conducted 6 and 10 months after the operation. In all cases, the implant was still effective.
In their battery of experiments, the researchers used positron emission tomography (PET) to measure rat brain activity during light sensitivity testing. Researchers then observed an increase in the activity of the primary visual cortex, the very cortex that processes visual information.
According to the researchers, the results tend to show that the implant directly activates residual neural circuits in the damaged retina. Further research is needed to understand exactly how this stimulation works at the biological level.
The authors of this study remain very optimistic and hope to be able to reproduce in humans the excellent results they obtained in rats. Grazia Pertile, one of the ophthalmologists who participated in this research, says : "We expect to conduct the first human trials in the second half of this year and to collect preliminary results during 2018. »
Source : Nature Materials
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