Helthcare & Wellness
Jul 1, 2017
SOLUTIONS AT SIGHT
One of the major causes of adult blindness in humans is the degeneration of photoreceptors in the retina. So far, there is no effective clinical treatment for these retinal disorders. But it seems this is about to change soon.
Scientists and ophthalmologists from the Italian Institute of Technology have developed a retinal implant that can restore lost vision. The procedure has proven its results in rats and later this year it will be tested in humans.
Let's start from the retina. It is located at the back of the eye and it is made up of millions of light-sensitive photoreceptors. Human beings are able to see due to these photoreceptors.
Mutations or injuries in any one of the 240 identified genes can lead to retinal degeneration, where these cells die off, even if the retinal neurons around them are unaffected.
Previous research has looked at treating retinitis pigmentosa with bionic devices which stimulate the fully intact and functional remaining nerves with lights. Other approaches focused on gene editing to repair the mutations that cause blindness.
The new approach led by the Italian team, proposes the implant of a prosthesis into the eye, which serves as a working replacement for the damaged retina.
The implant is made from a thin layer of conductive polymer, placed on a silk-based substrate and covered with a semiconducting polymer.
The semiconducting polymer absorbs the photons when light enters the lens of the eye and acts as a photovoltaic material. And when it happens, electricity stimulates the retinal neurons, filling in the gap left by the eye's natural but damaged photoreceptors.
The researchers implanted the artificial retina into the eyes of the rats, in order to test the procedure and take some conclusions. Thirty days after the operation, the rats eyes had healed and the tests began. The researchers wanted to test how sensitive they were to the exposure of light – called the pupillary reflex – and compare healthy and untreated against these operated rats.
First they exposed the animals to a low intensity light (one lux, no more than the light of a full moon) and the rats weren't much more responsive than untreated rats.
But as the light increased to four or five lux (pretty much similar to a dark twilight sky) the pupillary response of treated rats was indistinguishable from healthy animals. Six to ten months after surgery, the rats were tested again and the implant showed it was still effective.
The rats' brain was also monitored during the light sensitivity tests, using positron emission tomography, and the researches saw an increase activity of the primary visual cortex, which processes visual information.
They could then conclude that the implant directly activates residual neuronal circuitries in the degenerate retina. However, the reason how the stimulation works on a biological level is yet to explain.
And the researchers hope the results seen in rats will translate to people, something they're not sure yet. "We hope to replicate in humans the excellent results obtained in animal models", said ophthalmologist Grazia Pertile, one of the researchers. "We plan to carry out the first human trials in the second half of this year and gather preliminary results during 2018. This could be a turning point in the treatment of extremely debilitating retinal diseases", she concluded.