US researchers from Stanford University have developed a bionic eye, which has been successfully tested in rats. According to the research team, the eye implant - a 3-millimetre-wide chip that would fit behind the retina - could be a dramatic step above currently available technology.

Bionic Eye System (Courtesy: Stanford University)Published in the Journal of Neural Engineering, the system is a retinal prosthesis system that can stimulate the retina with resolution corresponding to a visual acuity of 20/80—sharp enough to orient yourself toward objects, recognize faces, read large fonts, watch TV and, perhaps most important, lead an independent life. The researchers tested the system in rats, but human trials are at least 3 years away.
Degenerative retinal diseases (such as age-related macular degeneration) is caused in 700,000 people each year in the USA alone. In such a disease, the rod-shaped photoreceptors at the retina's periphery (responsible for night vision), and cone-shaped cells (color vision) are damaged. However, the retina is still intact, and if it could be directly stimulated, some functionalities could be restored.
The complete setup includes a small chip implanted directly onto the eye, a wearable computer, a video camera, and a pair of infra-red goggles. First, light from (say) a flower enters the video camera. The video camera then sends the image of the flower to the wallet-sized computer for complex processing. The processor then wirelessly sends its image of the flower to an infrared LED-LCD screen mounted on the goggles. The transparent goggles reflect an infrared image into the eye and onto the retinal chip. The chip converts the image to the visual range, and projects it onto the retina.
This design employs a pixel density of up to 2,500 pixels per millimeter, corresponding to a visual acuity of 20/80, which could provide functional vision for reading books and using the computer. This is significantly better than the currently existing technologies, which provide only a few pixels per millimeter. The work is a synergy of diverse fields: biology, electronics, physics, and signal processing.