A therapeutic device comprising a first visual signaling element, a second visual signaling element positioned separately from the first visual signaling element, and a third visual signaling element positioned between the first and second visual signaling elements. A control apparatus controls the first, second and third signaling elements, and is arranged to alternately activate the first and second visual signaling elements for a first period of time, and to activate the third visual signaling element for a second period of time subsequent to the first period of time.
