In May this year, researchers announced that they had implanted two blind British patients with retinal prostheses, giving them vision for the first time in decades. What is this new technology and how has science fiction come so close to fact?
Scientists have attempted to restore sight to the blind for centuries. However, it was only in the 1990s that the technology really began to take shape. Now, there are at least 15 research groups around the world working on retinal prostheses.
Two conditions - retinitis pigmentosa and age-related macular degeneration - account for most blindness in the western world. They both affect the retina – the part at the back of the eye that absorbs light.
The retina makes an excellent target for a prosthetic implant because when just the outer layers are damaged, the nerves that process and carry the signals from the eye to the brain are still there and still work.
The job of the implant is to recreate the pulses that light usually generates in the retina, sending electrical impulses shooting down the optic nerve and into the visual cortex. And the result – vision. Just as Chris James experienced.
“As soon as I had this flash in my eye, this confirmed that my optic nerves are functioning properly, which is a really promising sign,” Chris said. “It was like someone taking a photo with a flashbulb, a pulsating light, I recognised it instantly.”
This description may sound disappointing after headlines like “Blind man can see again” but the technology is still in early, yet promising, days.
What’s more, researchers have found that the longer patients wear the device for, the better their vision becomes. They can start to make out shapes and outlines as the brain adapts to make sense of this new information.
“There are grounds to be cautiously optimistic and there is every reason to believe we are on the path to achieve this goal,” says researcher, Lofti Merabet of Harvard University.
The particular project that the British patients are involved in is by German company Retinal Implant AG and uses just one of several potential ways to target the retina.
Other devices in development differ in several features for example, where the implant sits (on the retina or within it); how much equipment sits outside the body (most need an external power supply, some need glasses); and what number of electrodes stimulates the retina (this dictates the resolution).
But what will it take for this technology to go from science’s vision to patients’ vision?
Firstly, studies will be needed to make sure that the prostheses are safe in the long-term and don’t do further damage to the retina. From a technical point of view, many of the devices in development have a limited number of electrodes. Increasing the number will give patients better resolution and more useful vision. Researchers will also need to learn more about how blindness and, equally, restoring sight change the brain.
This research has a long way to go, but for now there is light where before there was only darkness.
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