A 58-year-old blind man has been able to experience partial recovery of vision in one eye with the help of a breakthrough treatment using genetic engineering and light-activated therapy.
The treatment involved altering cells in the man's retina, a layer of tissue at the back of the eye that stopped working almost 40 years ago due to a neurodegenerative disease.
The patient, who remains unnamed, was diagnosed with retinitis pigmentosa (RP) as a teenager. RP is a condition where the cells in the retina that are receptive to light are broken down which can lead to complete blindness. It is the most common inherited eye condition, affecting around one in 4,000 people in the UK.
There is no approved treatment for RP, except for a gene-replacement therapy that only works on an early-onset form of the disease. The researchers said that while their findings, published in the journal Nature Medicine, are still in its early stages, their work could be seen as a stepping stone for new targeted treatments for those with RP.
To partially restore the patient's sight, researchers used a technique known as optogenetics to genetically alter nerve cells in the retina so that they would respond to light.
To do this, they used cells taken from green algae, a plant that has evolved to change the shape of its proteins in the absence, or presence, of different wavelengths of light.
After the algae's genetic information was injected into one eye, the man's retina began producing a protein, ChrimsonR, which responds to amber light. When ChrimsonR detected light within the amber wavelengths, it activated nerve cells in the eye which carried that signal all the way to the brain, where it was processed just like any other type of visual perception.
But now the team needed to turn the world amber.
They next developed specialised goggles that were fitted with a camera to capture and project visual images onto the retina at amber light wavelengths.
The patient was then trained for several months as the genetically-altered cells began to stabilise.
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Prior to the treatment, he could not visually detect any objects, nor could he do so without the goggles after the injection. However, a few months later, with the aid of the light-stimulating goggles, he was able to locate, recognise, touch and count objects such as notebooks, staple boxes and glass tumblers on a white table placed in front of him.
A tumbler was alternately taken on or off the table, and the patient had to press a button indicating whether it was present or absent.Results from the experiments showed he could tell with 78 per cent accuracy if the tumbler was present or not.
The team said their patient was “very excited” following his first experience partial vision after treatment when he observed the white stripes of a pedestrian crossing while out on the street.
“The findings provide proof of concept that using optogenetic therapy to partially restore vision is possible,” said Botond Roska, founding director at the Institute of Molecular and Clinical Ophthalmology Basel and professor at the University of Basel, Switzerland.
However, while this type of optogenetic therapy may be beneficial in restoring visual function in people with RP-related blindness, further results from this trial are needed for a clearer picture of the safety and efficacy of this approach.
“Importantly, blind patients with different kinds of neurodegenerative photoreceptor disease and a functional optic nerve will potentially be eligible for the treatment," said Jose-Alain Sahel, distinguished professor and chairman of ophthalmology at the University of Pittsburgh, US.
“However, it will take time until this therapy can be offered to patients.”
