VEP (Visual Evoked Potential)

An optical pathway from the eye to the occipital lobe of the brain is measured through Visual Evoked Potential (VEP). This test determines the integrity of the nerve transmission from the eye to the brain. A physician may recommend VEP tests when you complain of a change in your vision that may occur due to a problem in the optic nerve. 

A VEP test may help in diagnosing vision problems and associated causes, as follows:

• Loss of vision (with or without pain)
• Double vision
• Blurred vision
• Flashing lights
• Alterations in color vision
• Weakness of the eyes
• Weakness of arms/ legs (suspicion of multiple sclerosis) 

What happens during VEP?

Often, changes are too subtle and are only detected in the examination. VEP is useful for detecting optic nerve problems that general check-ups cannot diagnose. A checkerboard pattern or LED goggles are used as stimuli. During the test, signals are recorded from the posterior aspect of the scalp. 

Abnormality in waveform detects even subtle abnormality in the optic pathway.

VEP is used to check vision in children and adults unable to read eye charts. 

What does the VEP detect?

When light from an image enters your eye, it is converted into electrical energy at the retina and travels through the optic nerve to the visual cortex of the brain that processes vision. VEP measures neurological responses of the entire visual pathway by examining the electrical activity. It also measures the signal’s strength reaching your visual cortex and the speed it gets there. 

Instructions:

• Wash your hair the night before, and avoid applying hair chemicals, oils, and lotions.
• Make sure to have a sound sleep prior to the test.
• If you wear glasses, do bring them along with you during the test. 
• Eat a normal meal and take your usual medications prior to the test. 
• Any medications that may make you drowsy/ sleepy should be avoided.
• If you have any eye conditions, such as cataracts or glaucoma, that can affect the test should be informed to the doctor beforehand.