VEP is a non-invasive, electro-diagnostic device that is used to help objectively measure the function of the entire visual pathway from the eye to the visual cortex of the brain. It is painless and does not require dilation or sedation. It is also very helpful with non-verbal patients (whether infant or child with special needs). The VEP, measures how well visual information travels through the visual pathways to the brain and whether the information is processed equally through both eyes and the brain. The VEP can also help determine if a specific lens prescription will be able to make a change in visual function.