Two people with a rare heritage eye had their night vision restored thanks to experimental gene therapy, according to researchers.
These two people are part of a clinical test (opens in a new tab) test the safety and efficacy of the new gene therapy, the research team wrote in a report published in October in the journal iScience (opens in a new tab). These and other trials will need to be completed before the therapy can be approved for widespread use, but these early data suggest the treatment can stimulate “remarkable gains” in patients’ night vision, the scientists wrote.
Trial participants have a genetic condition called Leber congenital amaurosis (LCA), which affects about 3 in every 100,000 babies, according to University of Florida Health (opens in a new tab)one of the institutes involved in the development of the therapy.
The disease primarily affects the retina, the light-sensitive layers of nerve tissue at the back of the eye, and causes severe visual impairment, night or complete blindness within the first two years of life, often from the time of birth, according to Genetics and Rare Diseases Information Center (opens in a new tab). Different forms of ACL impact different genes involved in vision.
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The trial participants specifically have “LCA1”, which means they carry two faulty copies of a gene called GUCY2D, which codes for a protein. Normally, the photosensitive cells of the retina send an electrical signal to the brain after being exposed to light, and the encoded protein GUCY2D then helps reset the cells, preparing them to fire again. GUCY2D is especially important for rods, the light-sensitive cells that enable night vision, because it allows this cycle to take place even in the dark.
Without a working GUCY2D gene, this cycle stalls and cells can’t fire, according to the National Library of Medicine (opens in a new tab).
Although the cells cannot fire correctly, their actual structure and number remain largely unchanged. this is especially true of rods in the retina. (There are also cones in the retina, which enable color vision, but research suggests that people with ACL1 often have marked cone loss, the researchers noted in their report.)
In theory, feeding these rods a working copy of GUCY2D could restore their ability to fire, the researchers surmised.
To deliver a working copy of GUCY2D into the retina, the researchers placed the gene inside the protective shell of a modified adeno-associated virus, a type of virus that does not cause disease in humans. They then injected these DNA– carrier vessels under the retina; each participant received the treatment in only one eye, so their untreated second eye could be used as a point of comparison.
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Two participants, a 19-year-old man and a 32-year-old woman, received high doses of the treatment and are the subject of the iScience report. Before treatment, the two had limited daytime vision but virtually no night vision due to very low light sensitivity, about 10,000 to 100,000 times lower than normal levels, according to penn medicine (opens in a new tab)another institution involved in the trial.
Within eight days of treatment, the eyes of both participants became thousands of times more sensitive to light in low light conditions, and they showed improvement in the involuntary responses of the pupils to light and an improvement in their ability to navigate dark rooms. Three months after treatment, both patients’ rod sensitivity had continued to increase, and the woman’s had in fact approached normal levels.
These promising results come on top of additional data hinting at the efficacy of the treatment, which were presented at the American Academy of Ophthalmology (opens in a new tab) annual meeting in October. These earlier results showed that, in a total of 15 patients, the therapy caused minimal side effects, including transient side effects. inflammationand nine high-dose patients showed the most improvements in retinal sensitivity and vision.
But again, more research is needed before the Food and Drug Administration can evaluate the therapy for approval.
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