Visual Electrophysiology, comprises of a number of tests that
    investigate the visual pathways and retina.

    The Electro-retinogram (ERG)
    The ERG is a small response that is generated by the retina in
    response to light. Responses are recorded by a thread electrode
    placed along the lower eyelid. In small children disposable sticky
    electrodes are placed on the cheeks just below the eyes.

    Visual Evoked potentials (VEP) are recorded from small electrodes
    attached to the back of the head using a soft cream. The small
    electrodes are able to record very small responses generated by the
    visual cortex in response to visual stimulation.

    Electro oculogram is a response generated by the eyes as they
    move from one side to another. The response is recorded from
    disposable adhesive electrodes placed on either side of th eye.
The Electrophysiology Clinic 42 Harley St London