Visual evoked potential testing records electrical responses from the visual cortex after visual stimulation to assess conduction along the optic nerve and pathways. It is an objective measure of how quickly and strongly signals reach the brain.
Technique
Electrodes are placed on the scalp over the occipital region while the patient views pattern-reversal chequerboards or flashing lights. The resulting waveforms are averaged to reduce noise, and the latency and amplitude of key components are analysed.
- Conducted monocularly with appropriate refractive correction
- Pattern VEPs are sensitive to macular and optic nerve function
- Flash VEPs are useful when fixation is poor or in young children
- Testing requires cooperation but minimal verbal response
Clinical Role
VEPs assist in diagnosing optic neuritis, demyelinating disease, compressive optic neuropathies, and some congenital visual pathway disorders. Delayed or reduced responses indicate impaired conduction.
- Useful when structural imaging is normal but function is abnormal
- Serial tests can track recovery or progression
- Interpreted alongside visual acuity, fields, and imaging
- Abnormalities are not always specific, so correlation with clinical context is essential
