Last week we heard about the Argus II, a device that can restore partial sight to some blind people, and this week a new retinal prosthesis is promising to go one step further. While the Argus II relies on glasses, an externally-mounted video camera, and a separate processing box, the Alpha IMS system detects light coming into the eye via electrodes implanted underneath the patient's retina, before feeding it into a microchip that sends the signals to the brain. The brain then processes the data as it would organic signals from a healthy eye, and the patient sees a black and white image. There's also a dial fitted behind the ear for adjusting brightness, and the whole system is powered wirelessly by a pocket battery.
Developed by researchers at the University of Tübingen, Germany, the Alpha IMS has a few benefits over the Argus II. It has 1,500 electrodes compared to the Argus II's 60, offering much higher resolution and clarity. Because it's implanted behind the retina, patients can look around naturally by moving their eyes — the Argus II requires its wearer to turn their head. It's also able to take advantage of the "natural processing power" of the neurons in the retina, which help to process motion and contrast. The Alpha IMS can't help everyone, unfortunately. Only patients that lose vision through diseases that destroy the eye's light-detecting cells are able to benefit from the prosthesis — if the vision-processing parts of the nervous system are damaged then the device has nothing to send its data to.
Patients were able to recognize fine details like facial expressions
Nine patients have already been fitted with Alpha IMS prostheses, of which eight implants were successful. The final patient's optic nerve head was touched during surgery, resulting in implant failure. First-hand accounts from the patients successfully fitted with the implant have extremely encouraging. Close-up, previously-blind patients were able to detect mouth shapes such as smiles; the absence or presence of glasses on the face of a passer-by; objects such as telephones and cutlery; and even finer details such as signs on doors. In the far-vision range, patients could make out the horizon line, houses, trees, and rivers. Cars were located based on their bright reflections, while at night one patient was able to recognize moving cars by their headlights.
It's obviously early days for the Alpha IMS. Following the nine-patient pilot, additional testing has begun at centers in the UK, Hong Kong, and Hungary, with a focus on discerning the long-term stability and safety of the implant. Researchers are also hoping to develop teaching methods to help improve patients' visual recognition abilities.