Researching visual system for the blind. Blind man (left) and a researcher testing the TVSS (Tactile Vision Substitution System). TVSS was first developed by Professor Paul Bach-Y-Rita in 1972, and modern versions have since been designed. Input from a video camera (held in the blind man's left hand) is converted into output to an electro- tactile pad on the tongue (as here), or to a vibro-tactile back pad. The pad is pixellated and tingles the tongue, allowing the blind person to see by 'touch at a distance' (image of the water bottle is on the screen). The researcher is Stephane Maris, testing the Tongue Display Unit (TDU) at a research centre in Strasbourg, France.