Question
Because Video-ENG does not rely on the corneoretinal potential for recording, is it possible to perform Video ENG on blind patients?Answer
VNG is not going to help if the patient cannot foveate a target. However, if the patient is blind and able to foveate a target, and if the corneoretinal potential is too low to permit a quality ENG recording, then, I have found VNG to be superior. In our clinic we have established a normative data pool for a gross estimate of the corneoretinal potential strength. The value can be obtained by choosing ''Review calibration'' from the ICS Master menu. The value represents an estimate of the CRP required for +/- 10 degrees of calibration. As this value drops below 100 uV/10 degrees the quality of the recordings decreases precipitously and I begin to reach for VNG. In effect, the ICS system is automatically increasing the gain of the amplifiers to its limits and you begin to see noise floor (everything looks fuzzy). We are now looking at this value as a predictor of (primarily) retinal disease.
BIO:
Gary P. Jacobson, Ph.D. is Director of the Division of Audiology for the Henry Ford Health System. He is a past-president of the American Society of Neurophysiological Monitoring, current Editor of the American Journal of Audiology (AJA-ASHA) and is an Associate Editor (Electrophysiology) for the Journal of the American Academy of Audiology (JAAA). He serves on the Board of Directors and the Scientific Advisory Committee for the American Tinnitus Association. He is a co-editor of the text the ''Handbook of Balance Function Testing.''
