Visual Evoked Potential (VEP) testing is usually done by an ophthalmologist or a neurologist and is an evoked response caused by visual stimulus. The visual stimulant is usually flashing lights on the computer and is more sensitive compared to magnetic resonance imaging (MRI) in detecting lesions affecting the area in the optic pathway where the optic nerve crosses sides.
The Visual Evoked Potential (VEP) test may be recommended by your physician if you are experiencing changes in your vision that are potentially due to problems along nerve pathways. Some symptoms of those undergoing testing are noted as loss of vision, double vision, blurred vision, flashing lights, alterations in color vision, or weakness of the eyes, arms, or legs. The optical nerve helps transfer signals that allow us to see, so testing its usefulness will show problems that are often too subtle or not as easily detected during a routine clinical examination. Visual Evoked Potential (VEP) is commonly used in the diagnosis of Multiple Sclerosis (MS) because physicians can see the optic neuritis, associated with swelling and progressive destruction of the sheath covering the nerve, and sometimes the nerve cable. Abnormal VEP test results could also point to optic neuropathy, tumors or lesions compressing the optic nerve, or ocular hypertension which may later lead to Glaucoma. Because VEPs are very non-specific tests, a thorough patient history and examination are important for proper diagnosis.
Unlike other means of testing, the Visual Evoked Potential test is very non-invasive and one of the safest testing measures to date. It is a completely painless procedure with little to no complications experienced. Even those with Epilepsy can safely be exposed to the visual stimuli, as the VEP test is unlikely to set off any seizure activity. The first step to testing the optic nerve is the technician will adhere wires to your head that record brain waves and activity related to stimuli. Next, the technician will instruct you during the duration of the test, usually covering one eye at a time. For a Flash VEP, you will sit close to a machine with a light inside it and watch as it flashes. During a Pattern VEP, you will sit a little further back from a different machine that resembles a checkerboard on a computer. As the squares move and change in size, the signals from your brain will be recorded through the electrodes. After the testing is complete and the results are recorded, the technician will provide them to the requesting physician for further analysis and diagnosis. Overall, the testing takes about an hour and patients can return home safely the same day with little to no side effects.
Having clear results is critical to the test’s success. Some things you can do to prepare are washing your hair the night before and avoiding all chemicals, oils, and lotions at least 24 hours in advance. If you normally wear glasses or contact lenses, be sure to bring them to the test and let the technician know if you have any current eye conditions such as glaucoma or cataracts as these can affect the results. It should also be noted that patients are usually able to eat a normal meal and take medications prior to the test, but any medications that may make you drowsy should be avoided and talked about with your doctor prior to testing. The last thing that can best prepare you for a VEP test is a good night’s rest, arriving on time the day of, and relaxing before starting the test.
Have more questions? Feel free to contact your local Brain and Spine Specialists office to learn more about your upcoming Visual Evoked Potential (VEP).