An Assessment of the Technique and Clinical Application of Visual Evoked Response Measurements

Abstract

In this study an attempt has been made to review the clinical situation concerning the use of visual evoked response tests (VER). The literature reviewed has been selected mainly for the clinical applications of the technique and early classical work describing physiological concepts. In addition a study is made of the various derivations from the scalp made by different authors. In the material studied, stimulation was mainly by reversing checkerboard, but flash was used in some instances. A control series of 73 subjects, of age range 4-67 years, were divided into decades of age. Mean latencies of response and standard deviations were estimated. Amplitudes were also studied and found not to relate to age. The patients whose VER results are reported include a series of 150 with multiple sclerosis (MS) and retrobulbar neuritis (REN), independently classified according to McAlpine's criteria. Reports on the VER results in 24 patients with compressive lesions affecting the visual system are divided into pre-chiasmal, chiasmal, post-chiasmal and other intra-cranial sites. The VER of 17 patients with ischaemic disease is also reported and grouped according to the area affected by the ischaemia. Finally, there is a discussion on. the physiological basis of the VER with other electrophysiological tests, in particular the electroretinogram(ERG), Electromyogram (EMG) and the electro-encephalogram(EEG). Above all, it is emphasised that no one test gives the whole answer, and all must be assessed with the clinical findings in order to establish a diagnosis. Some thoughts on future developments of the technique are also presented.