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Videonystagmography is a collection of testing procedures that use the measurement of involuntary eye movements to diagnose certain balance or dizziness disorders. The test uses a special set of goggles that measures the eye movements of a patient when certain stimuli are applied, such as a changing of head positions or circulating fluid through a tube inserted into the ear canal. Once the series of tests using the goggles has been completed, a physician can determine if the cause of the disorder is the inner ear or some other physiological problem, such as a brain disorder or low blood pressure.
The use of goggles in videonystagmography has led to its widespread preference over electronystagmography. While both tests accomplish approximately the same end, electronystagmography requires the insertion of a number of electrodes into the muscles surrounding the eyes to measure their movement. Videonystagmography, on the other hand, uses a special set of goggles, which contains a set of infrared cameras that measure the same movements to a greater degree of accuracy. Due to the noninvasive nature of the goggles, patients are more comfortable during the test and less likely to make involuntary eye movements in response to discomfort caused by the electrodes. The combination of greater accuracy and fewer false eye movements has made videonystagmography the superior and preferred test.
A videonystagmography test is performed in four parts. The first portion of the test, ocular mobility, is designed to measure the voluntary ability of a patient to move his or her eyes. The patient will be asked to execute certain eye movements, such as to move them smoothly and slowly or to quickly jump from one place to another. The patient will also be asked to follow a target with his or her eyes as it maneuvers in specific patterns at specific rates of speed. By measuring the eye movements in this way, doctors can determine if the nerves and brain are operating properly.
In the second test, optokinetic nystagmus, the patient will be asked to follow a large moving image with his or her eyes. While similar to the ocular mobility test, this test is much more refined. The optokinetic nystagmus test is used to ensure the proper functioning of the central nervous system in relation to eye movement.
The third test that will be performed during a videonystagmography is the positional nystagmus test. During this test, the doctor or a technician will move the patient's head into different positions while measuring involuntary eye movement with the goggles. While the head is being moved, any abnormal movement of the fluid in the inner ear's semicircular canals, the organs that are used to create a sense of balance in humans, will cause the eyes to attempt to automatically readjust in an abnormal way. If the test proves positive, it demonstrates that tiny crystals in the fluid of the semicircular canals are causing the balance or dizziness problem.
Caloric testing is the final portion of the videonystagmography test. During this test, small tubes are inserted into the right and left ear canals, one at a time. Alternately warm and cold fluid is circulated through the tubes, which stimulates the inner ear. By measuring automatic eye movement in response to the fluid, and at different temperatures, this test can ensure that the eyes are responding properly to the stimuli or detect if there is an interconnection problem between the ears and eyes, which would manifest itself as dizziness or an inability to maintain balance.
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