What happens during a VEP test?

The procedure is very safe and non-invasive.

1. 1.Firstly, some wires will be glued to the top of your head to detect the brain waves.
   

2. 2.A technician will give you further instructions on what to do during the test. Normally, each eye will be tested separately.
   

3. 3.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.
   

4. 4.Readings will be recorded through the wires on top of your head.
   

5. 5.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.
   

6. 6.Usually the procedure takes about 45 minutes.
   

Side effects

There are rarely any side effects from this procedure. It is a painless procedure and apart from possible minor skin irritation from the electrodes, there are often no complications. If you have any medical conditions such as epilepsy, the visual stimuli you are exposed to is unlikely to set off seizure activity. This should however be noted with your doctor and technician before you undergo a VEP test.

After the procedure is done, patients normally return home on the same day. You should be able to drive home safely if you are feeling well after the procedure.

Factors influencing VEP

The cells within the part of your brain involved with vision are most sensitive to movement at the edges of your central visual fields. If you have poor vision, this does not seem to have too much effect on the response - larger checkerboard patterns can be used. Your gender, age and the size of your pupils are other factors that can affect the VEP. If you have taken any drugs that make you drowsy, or under the influence of any anaesthetic drugs, your VEP is also greatly affected.