A visual evoked response test measures the function of the optic nerve, the nerve that transmits messages from the eye to the brain. The test is most often used in the diagnosis of multiple sclerosis and can detect abnormalities even if visual symptoms are not apparent. The test records brain activity in response to a visual stimulus to find out the speed at which messages from the eye reach the brain. The test takes 20–30 minutes.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.