Visual Evoked Potentials (VEP)

Introduction

This leaflet is designed to give you some information about the investigation for which you have been referred. We hope it reassures you – we have an experienced team of experts who conduct these investigations. If after reading it you have any further questions or concerns, you will have the opportunity to discuss them on the day of the appointment before the tests start.

Consent

We must obtain your consent for any procedure or treatment beforehand. Staff will explain all the risks and benefits before they ask for your consent. If you are unsure about any aspect of the procedure or treatment proposed, please do not hesitate to ask them for more information.

What is a Visual Evoked Potential (VEP)?

Visual evoked potentials are signals produced by the brain in response to a visual stimulus. This test specifically assesses the function of your optic nerve, which is part of your visual pathway.

What is the reason for the test?

You have likely been referred for this test because you are having some problems with your vision. This test can be used to investigate if there is a problem along your visual pathway, that cannot be detected by other eye clinics.

What do I need to do on the day of the test?

There is no restriction on eating or drinking before, or after, the investigation.

Please continue taking any medication you are prescribed. It would be helpful to bring a list of your current medications with you.

Please bring your glasses or contact lenses with you.

It is important that your hair is clean; please do not use mousse, gel, oil or other hair products as this can affect the recording. Please try to avoid wearing lots of eye make-up, particularly mascara. Please do not wear fake eyelashes if possible.

What happens during the test?

A healthcare scientist will collect you from the waiting room and take you to the clinical room. They will explain the procedure and briefly test how well you can see. The healthcare scientist will measure your head with a tape measure and crayon then use a cotton bud and gritty paste to clean small areas of the scalp. A special sticky paste, similar to Vaseline, is then used to apply small silver discs called electrodes to the surface of the scalp. This is not painful, but does involve some rubbing. You will be given the opportunity to ask any questions you might have.

Once all the discs are on, you will be asked to look at a black and white pattern, like a checkerboard, one eye at a time. It is important that you remain awake during this as tiredness can affect the result.

Following this, it may be necessary to test the area at the back of your eye, called the retina. This test is known as a Pattern Electroretinogram (PERG). This is done by placing a very fine thread on your lower eyelid and asking you to look at the black and white pattern again.

You should expect to be in the department for approximately 1 hour.

Who will be present?

There will be one or two healthcare scientists present performing the test.

Addenbrooke’s is a teaching hospital and you may be asked if you would consent to trainee staff performing the test under supervision or if you would mind other healthcare professionals/students observing the test. Refusing consent for this will not affect your test.

We have no provision for accompanying children to be supervised whilst you are having this investigation.

Where is the test performed?

The test is performed at Addenbrooke’s Hospital. We perform this test in Clinic 33, which is located in the Addenbrookes Treatment Centre (ATC). Please see the instructions and map provided on how to find us.

Information on getting to Addenbrooke’s and different means of transport can be found at www.cuh.nhs.uk/finding-us (opens in a new tab)

What happens afterwards?

If you have no other appointments at the hospital you will be free to leave. The results will be sent to the consultant who referred you for the test.

Risks

There is a very small risk of mild skin abrasion due to preparation of the skin before applying the recording electrodes. Please inform the clinical healthcare scientist if you have any skin conditions, sensitive skin or any allergies.

Any questions?

If you have any questions or concerns before attending for this appointment, please ring us on 01223 216738 or 01223 348290. The department is open Monday-Friday 08.30-17.00. There is a voicemail service to leave a message if we are unavailable.

If your appointment is in Clinic 33 of the Addenbrooke’s Treatment Centre

We are on level 3 in the Addenbrooke’s Treatment Centre (ATC). We are at the end of the corridor, just before the double doors to Papworth Hospital. You will find us next to the Endoscopy department.

CUH Directions App

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My Chart:

We would encourage you to sign up for MyChart. This is the electronic patient portal at Cambridge University Hospitals that enables patients to securely access parts of their health record held within the hospital’s electronic patient record system (Epic). It is available via your home computer or mobile device

More information is available on our website: My Chart