Visual Evoked Potential Test
En Español (Spanish Version)

A visual evoked potential test (VEP) is used to look for problems in the brain that affect vision. A machine records brain waves related to the nerves that make up the visual pathway.

Optic Nerve and Muscles

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Reasons for Test
This test is often used to:

  • Diagnose and follow multiple sclerosis (MS)
  • Test vision in children and adults who are unable to read eye charts
There are many symptoms that might lead your doctor to order a VEP. You may be having double vision, blurred vision, or loss of part or all of your vision.

Possible Complications
There are no major complications associated with this procedure.

What to Expect
Prior to Test
You will be given instructions to prepare for the test, such as:

  • Wash your hair. Avoid hair chemicals such as hair sprays and gels.
  • Get a good night’s sleep.
  • Bring your corrective eyewear.
Description of Test
Wires will be attached to your scalp with tape. A patch will be placed over one eye. You will watch a screen with your other eye. The process is then repeated with the opposite eye covered.

The wires will be removed from your head.

After Test
You will be able to leave after the test is done.

How Long Will It Take?
About 45 minutes

Will It Hurt?

Your doctor will discuss the results with you and any further treatment that may be needed.

Call Your Doctor
Call your doctor if you have any concerns.

In case of an emergency, call for medical help right away.

National Eye Institute

National Multiple Sclerosis Society

Canadian Association of Optometrists

Canadian Ophthalmological Society

Evoked potentials. National Multiple Sclerosis Society website. Available at: Accessed July 17, 2014.

Evoked potentials studies. Johns Hopkins Medicine website. Available at:,P07658/. Accessed July 17, 2014.

Visually evoked potentials. Webvision website. Available at: Accessed July 17, 2014.

Last Reviewed June 2014

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