Artificial eye

A chip implanted directly into the visual cortex can restore rudimentary vision to the blind

Pop singer Stevie Wonder, who went blind shortly after birth and made news late last year after announcing his intention to get a retinal implant to regain his sight, will have to wait further for technological miracles, but for people who went blind later in life, another type of neurotechnology could be able to help them see again.

Artificial eye

Stevie Wonder must have been driven to his desire by exaggerated reports of technological advances, because retinal implants are being researched, but they have not yet been permanently implanted in humans. The microchips, which are connected to a tiny camera, can also only stimulate retinal cells that are still intact. The chips, which have only a few receptors, can restore only rudimentary vision, because the retina has more than a million nerve cells. Moreover, retinal implants seem to offer relief for only a few conditions, such as retinitis pigmentosa. People who, like Stevie Wonder, never learned to see "learned to see" could probably not do much with neuronal impulses that reach the brain via the optical nerve, because the brain does not know how to convert them into images.

From the Dobelle Institute, which also "neurological pacemakers" for respiration, pain relief and the urogenital system, has now unveiled a different neurotechnology in which a chip is implanted not in the retina but directly on the surface of the visual cortex. At least the permanent implantation of a chip has already been achieved here. As early as 1978, two blind people at Columbia-Presbyterian Medical Center in New York had the chips implanted, which are still in the brain. In one of the patients, a 62-year-old man who went completely blind at the age of 36, it has now been possible to use the "Dobelle Eye" and improved hardware and software, vision has now been restored in a narrow visual tunnel, allowing him to recognize even rough letters and move around a room.

The "Dobelle Eye" consists of a microcamera and an ultrasonic distance sensor mounted on a pair of glasses. The sensors are connected via a cable to a 2.5 kg mini-computer that the patient wears on a belt. After the data is processed by an imaging system and the image is simplified by removing noise, the electrical pulses are also transmitted via a cable to the chip, which is equipped with 68 platinum electrodes. Each of the electrodes can generate up to four phosphenes, which are placed on a black background surface of 20 x 5 cm for the patient. The changing light patterns thus produce a black-and-white image that one must first learn to interpret and which, of course, in no way approaches normal vision. Apparently, the main difficulty is the impression of depth, i.e. how far away something is, so that the patient still has to walk very carefully and stretch out one arm to avoid collisions.

After learning to use the system, the patient can now recognize letters with a coarseness of 5 centimeters at a distance of 1.5 meters: "Even though the chip creates tunnel vision with relatively few electrodes, the patient can navigate unfamiliar environments like New York’s subway system. By replacing the mini-camera with a special electronic interface, the patient can also learn to ‘see’ television images, use a computer and access the Internet." So far, however, the system is activated only two or three days a week in the lab. Later this year, an improved version of the "Dobelle Eye" will be launched on the market.