Superficial brain waves can be easily read from the scalp (see also EEG). These can be altered by various external stimuli. In this examination, a change in brain waves (potentials) is triggered (evoked) by visual stimuli.
When looking at an image, the retina is activated first. This transmits impulses via the optic nerve through the visual pathway in the brain to the visual cortex, which is located at the back of the head. In this examination, the patient sits in front of a screen that shows an alternating checkerboard pattern. During this examination, the patient should look intently at a marked point in the center. The resulting visual brain potential is derived from two electrodes attached to the head.
Based on the time-sequence and shape of the potentials, conclusions can then be drawn about the function of the pathways from the eye to the cortex and processing of signals in the brain. In various diseases (e.g. multiple sclerosis) these potentials can be pathologically altered.
The examination is harmless and non-painful. It takes about 15 minutes including preparation. The patient should be well rested and should bring their glasses.
