VISUAL EVOKED POTENTIAL (VEP)
A visual evoked potential is an evoked potential caused by a visual stimulus, such as an alternating checkerboard pattern on a computer screen. Responses are recorded from electrodes which originate from the occipital cortex – the area of the brain involv
- Loss of vision (this can be painful or non-painful);
- Double vision;
- Blurred vision;
- Flashing lights;
- Alterations in colour vision; or
- Weakness of the eyes, arms or legs.
- Wash your hairthe night before, but avoiding hair chemicals, oils and lotions.
- Make sure you get plenty of sleepthe night before.
- If you wear glasses, make sure you bring these along with you to the test.
- You are usually able to eat a normal mealand take your usual medications prior to the test. However any medications that may make you drowsy should be avoided.
- Arrive on time and try to relax before the test.
- On the day of the test, you should also let the technician know if you have any eye conditions such as cataracts or glaucoma as this can affect the test and should be noted in your records by the doctor.
The procedure is very safe and non-invasive.
- Firstly, some wireswill be glued to the top of your head to detect the brain waves.
- A technician will give you further instructions on what to do during the test. Normally, each eye will be tested separately.
- It is very important that you co-operate with the technician who conducts the test and be able to fix your vision in a certain spot. You will be asked to look at a screen similar to a television screen, with various visual patterns.
- Readings will be recorded through the wires on top of your head.
- After the procedure, the glue and wires are removed from your head. The doctor may discuss the results of the test with you after they have been analysed; otherwise the referring doctor will.
- Usually the procedure takes about 45 minutes.