Occupational Health

We represent several manufacturers that produce stand alone VNG systems as well as systems that combine VNG/ABR/OAE on the same notebook or desktop computer. Eye Dynamics offers VNG that is portable, fast and user friendly. It has options to add the VORT (vestibular ocular reflex test) test and a balance platform for the assessment of fall/risk factors and vestibular rehabilitation. Interacoustics VNG offers the most versatile software in terms of the stimulus, recordings and the variety of normative data presentations.

VORT TEST
The Vestibular Ocular Reflex Test monitors eye movement during active head rotation. This minimizes the need for expensive chairs that monitor passive rotation and incorporates the everyday movements and use of the head. The VORT permits for clinical evaluations of the vestibular – ocular reflex during and after the head movements.

The clinical assessment of vestibular disorders has undergone a revolution over the past several years due to the development and refinement of infrared video tracking technology. No longer is it necessary to use electrodes affixed to the patient to monitor eye movement. Now eye movement can be converted to a standard nystagmographic tracing by illuminating the eyes in a darkened environment with infrared light and then "locking on" to the pupil and tracking its movement throughout the "ENG" evaluation.

Video systems can be classified into one of two main categories. One includes the comprehensive diagnostic systems for performing a complete "ENG". THe other category is best described as "video frenzels".

Diagnostic VNG Test Systems
The traditional nystagmus-based tests (positional, Dix-Hallpike, caloric) are performed with the patient wearing "video goggles" having either one or two cameras attached. Since the patient's eyes are in a darkened enviroment fixation does not occur (most goggles do have a fixation light that can be turned on and off to provide a means for determining fixation suppression). Since the eyes are open throughout the test and displayed on a TV monitor the examiner can observe other eye movements that are pathological but many times are easily seen by reviewing the eye movement tracing. These include torsional or rotary eye movements that are common in benign paroxysmal positional vertigo, for example.

Oculomotor tests (saccade, gaze, tracking, optokinetic) are accomplished with either a digital light bar using video goggles with one eye covered, a headband with one or two cameras or a tabletop module into with the patient looks for presentation of the optical stimulus. The first two methods use a digital light bar to provide the stimulus.

Slow phase velocity is automatically calculated for all nystagmusbased tests as is unilateral weakness, directional preponderance and fixation suppression for the caloric tests. Analysis of the oculomotor tests are also automatically calculated and compared to reference data supplied by the manufacturer.

To summarize, the advantages of using video-tracking technology for the measurement of eye movement are:

Saves time, reduces costs and eliminates electrical and myogenic interference since electrodes are not used.
The eye/eyes can be displayed and videotaped throughout the examination for later review and for documentation in medical-legal cases.
Display and videotaping of eye movement allows for the observation and documentation of unusual yet pathologically significant eye movement such as torsional or rotatory nystagmus.
Test validity is enhanced since the entire test is performed with eyes open.
The video display portion of the system can be used during canolith repositioning maneuvers to document, via observaton and videotaping, the success of the treatment.

IA can assist in the selection of the instrument that is most suited for your needs, both clinically and financially.

For more information, contact Instrumentation Associates by phone at (800) 345-4790 by e-mail at jciarrochi@instrumentationassoc.com or use our Customer Contact Form, and a representative in our office will assist you.