Fig. 30. On-off response deficit in a patient with paraneoplastic night blindness with cutaneous malignant melanoma. The two upper tracings present the on and off responses of a patient with metatstatic cutaneous malignant melanoma. The on responses are greatly reduced as compared with responses of the right eye (OD) of a normal patient (lower tracing). (OS, left eye) (Courtesy of Philippe Kestelyn, University of Ghent, Belgium.)