Blindness affects about 0.7 per cent of Kenyans while 2.5 per cent of the population suffers visual impairment. After 40 years of blindness, a 58-year-old man can once again see images, thanks to an injection of light-sensitive proteins into his retina.
The study, published in Nature Medicine on May 24, is the first successful clinical application of optogenetics, in which flashes of light are used to control gene expression and neuron firing. The technique is widely used in laboratories to probe neural circuitry and is being investigated as a potential treatment for pain, blindness and brain disorders.
The clinical trial, run by GenSight Biologics in Paris, enrols people with retinitis pigmentosa (RP): a degenerative disease that kills off the eye’s photoreceptor cells, which are the first step in the visual pathway. In a healthy retina, photoreceptors detect light and send electrical signals to retinal ganglion cells (RGCs), which then transmit the signal to the brain.
GenSight’s optogenetic therapy skips the damaged photoreceptor cells by using a virus to deliver light-sensitive bacterial proteins into the RGCs, allowing them to detect images directly.
The researchers injected the virus into the eye of a man with RP, then waited four months for protein production by the RGCs to stabilise before testing his vision. They engineered a set of goggles that captured the visual information around him and optimised it for detection by the bacterial proteins.
Using a camera, the goggles analyse changes in contrast and brightness and convert them in real time into ‘starry’. When the light from these dots enters a person’s eye, it activates the proteins and causes the RGCs to send a signal to the brain, which resolves these patterns into an image.
The trial participant had to train with the goggles for several months before his brain adjusted to interpret the dots correctly. Eventually, he was able to make out high-contrast images, including objects on a table and the white stripes in a crosswalk.
When the researchers recorded his brain activity, they found that his visual cortex reacted to the image in the same way as it would have if he had normal sight.
With such a promising research outcome, Kenyan scientists should join the rest of the world and help our visually impaired and blind citizens to recover and enjoy life.