The pattern-induced flicker colours (PIFC), which belong to the subjective colours, are presented here as a method of investigating diseases of the eye and the visual track. Starting with Benham's top, new methods are elaborated for producing PIFC by means of rotating black and white discs and a computer-controlled black and white monitor. The investigations were performed in 40 normal and 111 pathological cases. A differentiation is made concerning the neuronal X-Y system. Different deficiencies result from different diseases. The PIFC are particularly suitable for the differential diagnosis of the neuritis nervi optici.