VEPs are the electrical response of the brain to a visual stimulus. To measure the response, three electrodes are placed on the scalp held on by a soft cream. Typically VEPs are recorded to a flashing strobe light, reversing and appearance black and white checkerboards. The pattern VEP is dominated by activity from the central 5 degrees, predominantly lower field. This macula predominance means that pattern VEPs in children can be used as an index of macula pathway function. Monocular stimulation with a trans-occipital array of electrodes, and where possible half field stimulation, can discriminate optic nerve, chiasmal and hemisphere anomalies. |