MONDAY May 24, 2021 (HealthDay News) – Doctors have for the first time used a form of gene therapy to restore partial vision in a blind person, according to results announced on Monday.
The research team genetically engineered retinal ganglion cells to become sensitive to light in a man whose vision was destroyed by retinitis pigmentosa, a genetic disease that breaks down cells that absorb and convert light into signals cerebral.
Using special glasses, the 58-year-old went from total blindness to being able to detect a large notebook, a small box of staples, glass cups and even the scratches of a crosswalk , researchers reported in the June issue of the journal. Nature medicine.
“This is the very first patient to report any improvement from optogenetics,” the gene therapy that made new cells sensitive to light, said lead researcher Dr Jose-Alain Sahel, president of ophthalmology at the University of Pittsburgh.
Dr Richard Rosen, head of retinal services at Mount Sinai Health System in New York City, called the news “very, very exciting.”
“It potentially works for the full range of patients who have these blinding diseases” involving retinal damage, said Rosen, who was not in the study.
The structure of the human retina is best described as inverted. Light-sensing photoreceptors are found at the back end of the retina, while ganglion cells at the front transmit visual information from the photoreceptors to the brain via the optic nerve.
The field of optogenetics involves the genetic alteration of cells so that they produce light-sensitive proteins called channelrhodopsins.
In this case, the researchers used optogenetics to make the top layer of ganglion cells photo-sensitive, bypassing the non-functional bottom layer of photoreceptors.
The researchers injected the human eye with a hollowed-out cold virus containing the genetic code for a channelrhodopsin called ChrimsonR, which is able to detect amber light.
After giving his retinas five months to accept the genetic alteration, they fitted him with a set of special glasses that projects visual images onto the retina at wavelengths of amber light.
The man had to train with the glasses on, but after seven months of training he spontaneously started reporting signs of visual improvement, Sahel said.
“The brain has to learn new language from the retina because what these ganglion cells tell the brain is not normal ganglion cell activity,” said lead researcher Dr Botond Roska, founding director of the ‘Institute of Molecular and Clinical Ophthalmology Basel in Switzerland.
Electroencephalogram (EEG) readings, which measure electrical activity in the brain, have shown that the human brain does respond to visual input from the eye.
“As a result, the retina is no longer blind,” Roska said.
Researchers have warned that human eyesight is not expected to recover enough to be able to read or recognize faces.
“To recognize a face you need very high resolution. This is not yet possible with the approach we are using, so we should not give anyone hope at this point that it will be able to read or recognize faces because for that you need a very high resolution, ”said Roska.
But the amount of vision the man got would be extremely important to the daily life of a blind person, Rosen said.
“These are people who are completely blind. There is nothing. They cannot see anything,” Rosen said. “If they could spot big obstacles in their path, that’s huge. Right now they are using a stick to see what is in their way. It is a small step, but it is also a big step for these patients.
More people have been injected with this gene therapy, researchers said, but the COVID-19 pandemic has hampered their ability to get to medical centers where they could train with special glasses.
“Due to COVID, only this patient was treated in time to be able to test the glasses and be trained and brought back to the hospital and tested properly,” Sahel said.
The man hopes to receive more training and ultimately use his restored vision as much as possible throughout his daily life, Sahel said.
Although excited by the report, Rosen urged for cautious optimism until more research is done on more patients.
“He’s a patient at this stage,” he said. “We don’t know how well that will work with others, and it’s something that will need to be refined, but the proof of concept is really spectacular.”
The National Eye Institute in the United States has more on retinitis pigmentosa, while Frontiers has more on optogenetics.
SOURCES: Jose-Alain Sahel, MD, president, ophthalmology, University of Pittsburgh; Richard Rosen, MD, chief of retinal services, Mount Sinai Health System, New York; Botond Roska, MD, PhD, Founding Director, Institute of Molecular and Clinical Ophthalmology Basel, Switzerland; Nature medicine, May 24, 2021
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