The Argus device relies on a video camera which is built into a pair of glasses to capture images.

These are converted into electrical signals which are transmitted wirelessly to an implant behind the retina.

The electrodes in the implant unscramble the signal to create a crude black and white picture, which is relayed along the optic nerve to the brain.

Linda Moorfoot is one of the few patients to be fitted with the implant. She had been totally blind for more than a decade with the inherited condition retinitis pigmentosa.