Visual Evoked Potential Test
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Visual Evoked Potential Test


En Español (Spanish Version)


This test is used to diagnose brain defects that affect the vision nerves. It is similar to an electroencephalogram (EEG) in that it records brain waves. It differs in that it focuses specifically on the parts of the brain that involve vision. Since the visual nerves run the entire length of the head, this test can evaluate a large part of the brain.

Optic Nerve and Muscles


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Parts of the Body Involved

  • Eyes
  • Brain

Reasons for Procedure

This test is often used to diagnose and follow multiple sclerosis . It can also detect brain tumors, injuries, and strokes . Additionally, it can be used to test vision in children and adults who are unable to read eye charts.

Because the brain has so many different functions, there are many symptoms that might lead your doctor to order a visual evoked potential test. You may be having double vision, blurred vision, or loss of part or all of your vision. You may have suffered an eye or head injury. You may be experiencing weakness of your eyes, arms, or legs.

Risk Factors for Complications During the Procedure

This procedure is completely safe and noninvasive.

What to Expect

Prior to Procedure

You will be given instructions to prepare for the test, including washing your hair but avoiding hair chemicals, getting a good night’s sleep, and bringing your corrective eyewear.



Description of the Procedure

Wires will be attached to your scalp with adhesive to detect brain waves. Each eye will be tested separately while the other is patched. All you need to do is look at a television screen.

After Procedure

The adhesive and wires will be cleaned from your head. Your doctor will discuss the results with you after they are analyzed.

How Long Will It Take?

This test takes about 45 minutes to perform.

Will It Hurt?


Possible Complications

None, other than mild skin irritation from the electrodes

Average Hospital Stay

None. The test can be done without hospitalization.

Postoperative Care



Results will indicate what further treatment is needed.

Call Your Doctor If Any of the Following Occurs

No complications are expected.


The National Multiple Sclerosis Society

University of Michigan Health System


BC Health Guide

University of Ottawa Eye Institute


Evoked potential studies. St. John's Mercy Healthcare website. Available at: http://www.stjohnsmercy.org/healthinfo/test/neuro/TP014.asp . Accessed September 8, 2005.

Merck Medicus website. Available at: http://www.merckmedicus.com/pp/us/hcp/thcp_raj_content.jsp?pg=/ppdocs/us/hcp/content/raj/chapters/raj-ch-026-s003.htm . Accessed September 8, 2005.

Last reviewed December 2007 by Alexander J. Anetakis, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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