A man blind with retinitis pigmentosa has had glimmers of vision restored using a high-tech treatment using optogenetics, which involves genetically altering nerve cells so they respond to light.
French firm GenSight Biologics has published results in Nature Medicine showing that the first recipient of its treatment can recognise different objects in lab tests. “It’s exciting to see the first publication on human optogenetics,” says Ed Boyden at the Massachusetts Institute of Technology in Boston, a co-inventor of optogenetics, in New Scientist.
Optogenetics has become a widely used lab tool, because it allows precision control over brain cells by altering them so they fire in response to light. It was thought to have limited medical potential for treating brain disorders in people, because getting light inside the head requires implanting a fibre optic cable.
Several groups are trying to develop it as a treatment for blindness. One targeted condition is retinitis pigmentosa, an inherited disease in which the retina, a disc of tissue at the back of the eye, gradually deteriorates and the light-detecting cells die.
With GenSight’s therapy, the nerve cells underneath the light-detecting layer are injected with a gene originally found in algae, which makes them fire in response to amber light. To be able to see, the recipients need to wear goggles with cameras and processors that turn ordinary light into amber wavelengths, and boost the signal so it can be detected by the altered cells.
The first person to get this treatment, a 58-year-old man from Brittany in France, found that after about a year, he could see the black and white stripes of pedestrian crossings on the road.
Since then, he has become able to perceive objects like a phone, furniture or a door in a corridor. In lab tests, he was able to count and locate objects in front of him – but he can’t recognise faces.
The man’s vision may improve further, because it takes time for the brain to learn to process the unusual signals from the eyes, says José-Alain Sahel at the Vision Institute in Paris, who is working with the GenSight team.
In its current form, the approach may not give good-enough vision to allow reading or recognising faces, says team member Botond Roska at the Institute of Molecular and Clinical Ophthalmology in Basel, Switzerland. “For that you need very high resolution.”
A US firm Bionic Sight, reported in March that four people who had been blind or nearly blind could now perceive light and motion of objects in front of them thanks to its optogenetic treatment, but hasn’t yet published a scientific paper on these findings.
Even small improvements in vision may have a large impact for someone who is nearly blind, says Michel Michaelides at University College London, who is developing a different kind of gene therapy for blindness.
Study Details
Partial recovery of visual function in a blind patient after optogenetic therapy
Authors: José-Alain Sahel, Elise Boulanger-Scemama, Chloé Pagot, Angelo Arleo, Francesco Galluppi, Joseph N. Martel, Simona Degli Esposti, Alexandre Delaux, Jean-Baptiste de Saint Aubert, Caroline de Montleau, Emmanuel Gutman, Isabelle Audo, Jens Duebel, Serge Picaud, Deniz Dalkara, Laure Blouin, Magali Taiel & Botond Roska
Published in Nature Medicine on 21 May 2021
Abstract
Optogenetics may enable mutation-independent, circuit-specific restoration of neuronal function in neurological diseases. Retinitis pigmentosa is a neurodegenerative eye disease where loss of photoreceptors can lead to complete blindness. In a blind patient, we combined intraocular injection of an adeno-associated viral vector encoding ChrimsonR with light stimulation via engineered goggles. The goggles detect local changes in light intensity and project corresponding light pulses onto the retina in real time to activate optogenetically transduced retinal ganglion cells. The patient perceived, located, counted and touched different objects using the vector-treated eye alone while wearing the goggles. During visual perception, multichannel electroencephalographic recordings revealed object-related activity above the visual cortex. The patient could not visually detect any objects before injection with or without the goggles or after injection without the goggles. This is the first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy.
Full Nature Medicine study (Open access)
Full BionicSight statement on US trial (Open access)