Progress during the last 60 years has revealed numerous electrical signals arising from many parts of the visual system. These now play an essential part in the detection of many pathological conditions. Further progress in the acquisition and interpretation of these signals is necessary however before they could be justified as part of every routine eye examination. Such significant progress is only likely to occur if the electrophysiological origins of each signal can be more precisely identified and understood. Fundamental research on many aspects is therefore necessary.