Researchers at the Institute for Ophthalmic Research at the University of Tübingen, Germany, have restored vision in nine blind patients suffering from retinitis pigmentosa using tiny retinal implants embedded in the eye.
Nine patients were chosen because they had all suffered hereditary diseases where the retina had degenerated to the point of blindness, but left the remainder of the visual pathway intact. Eight of the nine could still detect some light, although could not locate its source. One was completely blind.
Each was implanted with a tiny 3x3mm film square containing 1,500 photodiodes which send out electrical signals when they detect light. The electrical signals are picked up by the nerve cells lying against the retina and passed to the brain. When the retina implant is switched on, the patients perceive a pixellated diamond in the center of vision, 15 degrees wide.
Light entering the eye does not contain enough energy to power the electrical pulses from the device, so the retinal implant must rely upon an external power source to amplify the signal.
A foil strip just 17μm thick exits through the eye and connects to a power cable that travels under the skin to a coil behind the ear. Another coil connected to a power supply attaches magnetically to this point and supplies power via transdermic induction – i.e. through the skin. The power supply also has controls which can be used to adjust the contrast and brightness of the retinal signals.
Two thirds of the patients experienced significant improvement in their vision.
However, to the patients themselves, the difference was often dramatic. They reported being able to see people again, objects in a room, food on their plate, colleagues at work and of being able to recognize faces and smiles. Below, one of the patients talks about his experiences with the implant. “For the first time,” he says, “I could see everything.
Professor Eberhart Zrenner, of Tubingen University’s Institute for Ophthalmic Research, said trials ‘exceeded expectations’
He said: ‘As physicians we are constantly seeking out the best treatment options for our most in-need patients which most definitely includes those suffering from advanced-stage retinitis pigmentosa.
‘This research provides additional evidence our sub-retinal implant technology can help some patients with retinal degeneration regain functional vision and does so in a way that does not require externally visible equipment.’
RP is a disease that mainly affects the retina – specifically, the photoreceptors in the macular layer, which slowly degrade until the patient goes blind.
Although the disease is incurable, the nerves of the retina remain functional in one bright spot. If these nerves can be stimulated then some form of vision might be recovered.