Many people with PD have difficulty initiating and sustaining walking in conditions which would normally present no problems (such as an unobstructed corridor). The degree of these mobility difficulties can vary with the subject, the time of day and the stage of disease but are always accompanied by severe loss in quality of life. Typically when people with PD can only move very slowly or completely freeze (phases called “bradykinesia” and “akinesia” respectively) they feel vulnerable and isolated. Accompanying symptoms include an expressionless “masked” face, a weak voice and bent posture. Social interaction becomes extremely difficult and each year many deaths and injuries occur as people with PD attempt to move whilst in this state.

Paradoxically, when visual “obstructions” are placed in their way, a small proportion of people with PD undergo a dramatic release from these symptoms and can suddenly stand up straight, speak strongly and walk normally: an effect called kinesia paradoxa. These “obstructions” can be as simple as pieces of paper set down on the floor and are usually referred to as visual “cues”.

The physiological mechanisms of kinesia paradoxa are not understood and until recently there was little opportunity to analyse it or exploit it. However, technology has now evolved to the point where a user, wearing adapted glasses, can see visual cues, such as virtual “pieces of paper” wherever they looked whilst continuing to negotiate the real world, interacting normally with other people. This allows certain people with PD to walk, to talk and to socialise where before they were effectively paralysed.

INDIGO moving visual cues in the user’s peripheral visual field within specially adapted glasses running MPEG video software on dedicated portable hardware.