THE ESSENTIAL
- In people with color blindness, the cone cells do not send signals to the brain, but a good number of them remain present.
- For the other two children, the researchers say they cannot confirm whether the treatment was ineffective, whether there are treatment effects that were missed by the tests, or whether the effects are delayed.
To date, there is no treatment to cure color blindness. Scientists from University College London (UCL) have thus decided to carry out work to find out if gene therapy, consisting of introducing genetic material into cells to treat a disease, was effective in combating achromatopsia. As a reminder, it is an inherited retinal disease, which disrupts the function of the cones (responsible for color perception) from birth and leaves patients with complete color blindness, low acuity, photosensitivity and nystagmus ( or uncontrolled eye movement).
“Recent advances in gene therapy have brought the treatment of previously incurable eye diseases within reach. While the success of gene replacement therapy in non-primate models with color blindness has raised many hopes for clinical treatment , it remained to be determined whether and how these therapies could restore cone function in the brains of human beings.” the researchers said.
Four children followed
For the purposes of research published in the journal Brain, the authors recruited four children, aged 10 to 15, with achromatopsia. The young patients participated in two trials at the same time. The latter were testing gene therapies targeting specific genes known to be involved in color blindness.
The researchers used a functional magnetic resonance imaging (fMRI) mapping approach to separate emergent cone signals after processing from existing cone-generated signals in patients. This allowed the researchers to attribute any changes in visual function, after treatment, directly to the targeted cone photoreceptor system. Then, the data was compared to tests involving nine untreated patients and 28 volunteers with normal vision.
“Taking advantage of the plasticity of our brain”
According to the results, two of the four children showed signs of new cone-generated signals in the visual cortex of the brain from the treated eye, six to 14 months after treatment. “Importantly, this change was associated with significantly improved psychophysical measures of cone-mediated visual function,” can we read in the study.
“We demonstrate that it is possible to take advantage of the plasticity of our brain, which may be particularly able to adapt to the effects of treatment when people are young. Our study is the first to directly confirm widely held speculation that which gene therapy offered to children and adolescents may successfully activate dormant cone photoreceptor pathways and evoke visual cues that these patients have never experienced before,” said Tessa M. Dekker, lead author of the work, in a statement.
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