Visual acuity, vision for detail and patterns, may be measured using the VEP. In adults, visual acuity is measured with the letter chart. For those who are unable to read the letter chart, the VEP is an option or may be used. It measures acuity by assessing the response of the vision part of the brain to alternating black and white stripes. This acuity test is most helpful in those youngsters for whom other vision tests, like the preferential looking test, give ambiguous or incomplete information about visual acuity.

To do the test, small metal discs the size of a small finger nail are placed on the head. The discs are connected by small wires to the computer held in place by a paste (similar to toothpaste). Three discs are placed at the back of the head (over the visual cortex), one on the top, and one on the forehead. A band is wrapped around the child's head to hold the electrodes in place during the test.

The child is then positioned to view a TV screen displaying alternating black and white stripes that progressively get thinner. As the child views the stripes, a signal is relayed to the visual cortex and detected by the electrodes. The test is designed to find the finest black and white stripes that produce a reliable response.

The tests take about an hour, depending on the child's attention or behavior. Sometimes it is necessary to test the vision of each eye separately. In such a situation, a patch is used. After the recordings are completed, the records are analyzed and the final results are included in a written report of the visit.