Description
Many larger eye units now have the facility to measure the electrical changes, which accompany visual stimuli. These electrical changes to light or patterns can be recorded from the eye through electrodes placed on the skin of the eyelids or from an electrode incorporated into a contact lens; they can be recorded from the visual cortex through electrodes placed on the skin of the scalp. The electrical responses of the eye (electro-oculogram and electroretinogram) are known to arise from the retina whereas those from the brain (visually evoked potential) have a more complex origin. A visual stimulus can produce simultaneous activity in many different visual areas of the brain and the particular area can vary depending on the nature of the stimulus. Since the initial signals come from the eye it is important that eye disease is detected and diagnosed before interpreting responses from the brain or visual pathway.
