A group of scientists published in the journal Nature Medicine a report on the successful completion of an experiment to restore partial vision, reports The New York Times. The patient's vision, a 58-year-old Frenchman, is still far from ideal, and he has to constantly wear glasses. However, the success of the experiment is proof that blindness can be fought.
When light enters the eye, it is captured by so-called photoreceptor cells. The photoreceptors then send an electrical signal to their neighbors, the ganglion cells, which can identify functions such as movement and send their own signals to the optic nerve, which carries information to the brain.
People who have inherited genetic forms of blindness are virtually immune to treatment because they completely lose their photoreceptors: their eyes lack the proteins needed to see. To solve the problem, the researchers tried to convert ganglion cells into photoreceptor cells. They used proteins derived from algae, which can make any nerve cell sensitive to light.
In the early 2000s, neuroscientists succeeded in introducing such proteins into the brain cells of mice and other laboratory animals by introducing modified viruses that carry their genes. The viruses infected certain types of brain cells, which then used the new gene to build light-sensitive channels.
This technique, called optogenetics, was originally used to study how the brain works. The authors of the new experiment tried to apply optogenetics to add light-sensitive proteins to the cells of the retina. After all, retinal cells are also nerves - that is, an extension of the brain.
Scientists have chosen an optogenetic protein that is sensitive to yellow light - it affects the eyes more easily than others. It was delivered to the ganglion cells of the retina by viruses.
The researchers also created a special device for converting visual information from the outside world into yellow light that can be recognized by ganglion cells. They created glasses that scan the field of view thousands of times per second and register any pixels that change the light: a pulse of yellow light from this pixel is sent into the eye. According to the researchers, in this way the brain can create images. But are blind people able to use this information to recognize objects? It was questionable.
After testing their gene therapy and safety glasses on monkeys, the scientists tested it on a man, a 58-year-old blind Frenchman. 40 years ago, at the age of 18, a man was diagnosed with retinitis pigmentosa - he had defective genes that, due to mutations, cause destruction of light-sensitive cells in the retina. Scientists injected the patient with gene viruses into one eye, and after a few months, during which optogenetic proteins were to grow in ganglion cells, they taught him to use glasses. After seven months of wearing glasses at home and on walks, the patient realized that he saw the lanes of a pedestrian crossing, and during laboratory tests he could reach out and touch a notebook lying on the table. In some tests, the man wore electrodes on his head that detected brain activity. When the glasses sent signals to the retina, the areas of the brain involved in vision were activated.
This man's vision is still rather limited: he can only see monochromatic images and at a fairly low resolution. However, the results prove that optogenetic therapy can partially restore vision.
Researchers are now testing higher doses of the virus and improving glasses: they should be more comfortable and deliver more information to the retina. In addition, they are trying to find optogenetic proteins that would help retinal cells become sensitive enough to detect light without glasses.