It’s a known fact, that one of the leading causes of vision impairment and blindness in the world is Retinal degeneration. About two of the most common retinal degeneration diseases are age-related macular degeneration (AMD) and retinitis pigmentosa (RP). AMD affects more than 2 million people in the U.S while RP affects roughly 1 in 4,000.
Both conditions cause loss of vision by damaging the photoreceptor neurons in the retina — as the inability to perceive light is what leads to loss of sight.
Currently, a team of researchers, led by the Italian Institute of Technology, is developing a new method of treating retinal degeneration, this was achieved using a prosthesis implanted into the retina. It’s made from a thin layer of conductive polymer which is placed on silk-based substrate. It is then covered by a semiconducting polymer which acts as a photovoltaic material, capable of replicating the function of the damaged photoreceptors. As soon as light enters the eye, this device absorbs photons and the resulting electricity stimulates the retinal neurons. They have successfully tested this retinal implant on rats, and detailed their research in the journal Nature Materials.
The team used lab-grown rodents — named Royal College of Surgeons (RCS) rats — which are bred to develop the rat-version of retinal degeneration. Weeks after these RCS rats were given the new retinal implants, the researchers tested them for pupillary reflex to determine how sensitive they were to light. The researchers found that the treated rats response to light with 4-5 lux medium intensity showed pupillary responses similar to those in healthy rats.
After the surgery the researchers tested the rats 6 months later, then again 10 months and concluded that the responses were the same, this proved that the implant’s effect could actually last longer than expected. Although similar to the healthy rats, the treated RCS rats were shown to suffer some vision impairment due to aging.
“Electrophysiological and behavioral analyses reveal a prosthesis-dependent recovery of light sensitivity and visual acuity that persists up to 6–10 months after surgery.”
In order to make sure that the treated RCS rats were indeed capable of perceiving light, the researchers subjected their brains to positron emission tomography (PET) scans, which revealed that there was an increase in the activity of the brain’s primary visual cortex – a part responsible for processing visual information, “The rescue of the visual function is accompanied by an increase in the basal metabolic activity of the primary visual cortex, as demonstrated by positron emission tomography imaging,” the team reported.
Even though the treated RCS rats could technically see again, further research is still needed because the researchers aren’t exactly sure how it works and whether the same success could be achieved in humans.
Ophthalmologist Grazia Pertile said “We hope to replicate in humans the 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.”
The retina is the third and inner coat of the eye which is a light-sensitive layer of tissue. The optics of the eye create an image of the visual world on the retina (through the cornea and lens), which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centres of the brain through the fibres of the optic nerve. Neural retina typically refers to three layers of neural cells (photo receptor cells, bipolar cells, and ganglion cells) within the retina, while the entire retina refers to these three layers plus a layer of pigmented epithelial cells.