As odd as it probably sounds, the eyes are closely linked to the ears, and they depend on each other for a good balance and clear vision. Head movement and other stimulation of the inner ears send signals to the muscles to the eyes via the nervous system. The technical name for this anatomic function is the vestibulo-ocular reflex (VOR).
The VOR normally generates eye movements that maintain clear vision as your head moves. During several kinds of tests, health professionals stimulate your inner ears in controlled ways and measure the involuntary eye movements (nystagmus) caused by this stimulation.
“VNG/ENG” is a group or battery of eye movement tests that look for signs of vestibular dysfunction or neurological problems. Although called videonystagmography or electronystagmography, the VNG/ENG can measure more than just nystagmus (a kind of involuntary eye movements). It can also record other eye movements to evaluate some brain functions. VNG/ENG tests are probably the most common of the tests administered to people with dizziness, vertigo, and/or balance disorders.
During a group of VNG/ENG tests, your eye movements will be recorded and analysed by infrared video while you wear special goggles. A small percentage of patients cannot be tested with the infrared video method. These people will be tested with small electrodes on the skin around the eyes used for recording eye movements instead. The electrodes attach to your skin with an adhesive, much like a small bandage.
During testing, the audiologist will ask you to name names or do simple math. This is to keep your mind alert and busy during the testing.
One VNG/ENG test included an evaluation of the movement of your eyes as they follow a moving target. Another obverses eye movements as your head is positioned in different directions. During the caloric test cool and warm air is blown into your ear canal and onto the ear drum. Changes in the air temperature stimulate the inner ear and test the eye movement (nystagmus) response generated by the stimulation.
Other VNG/ENG tests might include visual tracking (sometimes called visual-ocular control), optokinetic nystagmus, gaze, spontaneous nystagmus, saccades, smooth pursuit, positional, positioning (Dix-Hallpike), fistula or pressure, head shaking, and head thrust.