A silicon chip that faithfully mimics the neural circuitry of a real retina could lead to better bionic eyes for those with vision loss, researchers claim. About 700,000 people in the developed world are diagnosed with age-related macular degeneration each year, and 1.5 million people worldwide suffer from a disease called retinitis pigmentosa. In both of these diseases, retinal cells, which convert light into nerve impulses at the back of the eye, gradually die. Most artificial retinas connect an external camera to an implant behind the eye via a computer (see 'Bionic' eye may help reverse blindness). The new silicon...