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Monday, October 23rd 2006

An Implantable Artificial Eye

Previous attempts to restore some sight to those suffering retinal blindness involved external cameras and computers, but scientists are hopeful for a new implantable “retina chip.”

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 chip created by Kareem Zaghloul at the University of Pennsylvania, US, and colleague Kwabena Boahen at Stanford University, also in the US, could remove the need for a camera and external computer altogether.

The circuit was built with the mammalian retina as its blueprint. The chip contains light sensors and circuitry that functions in much the same way as nerves in a real retina – they automatically filter the mass of visual data collected by the eye to leave only what the brain uses to build a picture of the world.

“It has potential as a neuroprosthetic that can be fully implanted,” Zaghloul told New Scientist. The chip could be embedded directly into the eye and connected to the nerves that carry signals to the brain’s visual cortex.

To make the chip, the team first created a model of how light-sensitive neurons and other nerve cells in the retina connect to process light. They made a silicon version using manufacturing techniques already employed in the computer chip industry.

Their chip measures 3.5 x 3.3 millimetres and contains 5760 silicon phototransistors, which take the place of light-sensitive neurons in a living retina. These are connected up to 3600 transistors, which mimic the nerve cells that process light information and pass it on to the brain for higher processing. There are 13 different types of transistor, each with slightly different performance, mimicking different types of actual nerve cells.

Too cool.

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