Visual Evoked potentials are responses generated in the brain  as a
    result of stimulation of the visual pathways. These responses can be
    recorded from the scalp by small electrodes attached to the head by a
    When a pattern stimulus is used the size of the squares can be made
    smaller and smaller until the response disappears. The last checks
    size to generate a response is then used to give an indicator as to
    how well the baby is seeing.
The Electrophysiology Clinic 42 Harley Street London