Scientists have developed a groundbreaking gene therapy treatment that has improved night vision in adults with congenital blindness. According to the researchers, patients with congenital blindness caused by GUCY2D mutations experienced striking recoveries within days of the treatment.
The science and other stuff to know
In a study published in the journal ScienceDirect, researchers at the Scheie Eye Institute in the Perelman School of Medicine at the University of Pennsylvania studied two patients with Leber Congenital Amaurosis (LCA). This is an eye disorder that’s present from birth (congenital). The condition affects both the peripheral rod cells, which allow you to see at night, and the central cone cells, responsible for fine detail and color vision. People with this disorder typically have severe visual impairment beginning at birth or shortly afterward. Typically, the visual impairment tends to worsen over time.
In an attempt to treat LCA caused by mutations in the gene GUCY2D, researchers administered AAV gene therapy, which carries the DNA of the gene’s healthy version, into the retina of one eye for each of the patients, the press release explains. Within days of the treatment, each patient displayed significant improvements in rod-type photoreceptor cell-mediated visual functions in the treated eye. Both patients had large deficits in rod photoreceptor-based night vision before the treatment.
“These exciting results demonstrate that the basic molecular machinery of phototransduction remains largely intact in some cases of LCA, and thus can be amenable to gene therapy even after decades of blindness,” said study lead author Samuel G. Jacobson, MD, Ph.D., a professor of Ophthalmology at Penn.
Children born with LCA have light-gathering cells (rods and cones) of the retina that don’t function properly. This research shows that by administering a high dosage of AAV gene therapy into the eyes, patients with mutations in the GUCY2D can achieve improved night vision.
“Tests showed that both patients’ treated eyes increased their sensitivity to light by thousands of times in low light, significantly reversing the initial visual abnormalities,” the study notes. This offers hope to people living with LCA caused by GUCY2D mutation.
Up to 20 percent of LCA cases are caused by mutations in GUCY2D. This gene is responsible for transforming light into neural signals in retinal photoreceptor cells. Prior studies have shown that patients with this form of LCA tend to have relatively preserved photoreceptor cells, hinting that rod-based phototransduction could work again if functional GUCY2D were present. A gene therapy, Luxturna, is currently available for LCA caused by two mutations in a gene called RPE65.