A subretinal microchip implant has entered new clinical trials in the United Kingdom and Hong Kong, and early results are encouraging. The technology is important because until now, vision loss from retinitis pigmentosa, a genetic disorder that frequently leads to blindness, has been considered permanent. More than 200,000 people in the U.S and Europe suffer from the disease at this time.
Retinitis pigmentosa is a progressive genetic disorder that causes an imbalance of proteins to be produced by photoreceptor cells. This limits the retina’s ability to produce eyesight, and the cells die gradually, eventually leading to blindness. Antioxidants such as vitamin A palmitate may slow the disease, but they cannot restore lost vision.
Researchers believe that the microchip technology will work because inner retinal nerve cells continue to function even after vision has been lost. For this reason, 2 approaches have been explored to restore vision; (1) epiretinal implantation of electrode arrays which interfere with retinal ganglion cells forming the retinal output pathway, requiring external image and processing because it bypasses retinal image analysis. The clinical trials in the United Kingdom and Hong Kong involve the (2) approach, the implantation of a 3x3mm, 1500-electrode microchip below the retina, in the macular region. This type of microchip senses the light of an image and translates it, point by point, into small currents proportional to the light. Each electrode contains a photodiode amplifier electrode set within a single pixel that stimulates nearby neurons, closely resembling normal visula signals.
The operation takes about 9 hours and requires maxillofacial surgeions; ear, nose, and throat surgeons; and ophthalmic surgeons.