Corneoretinal potential variations: significance in electronystagmography.

Spontaneous variations in the corneoretinal potential (CRP) may introduce large errors when using electronystagmography (ENG) to measure responses during clinical caloric testing. Whether or not conventional calibration techniques are adequate to control such measurement errors has not been established. We studied CRP variations in normal subjects and patients by measuring calibration before and after a series of caloric tests. Among patients the CRP either rose or fell in a random manner; we were unable to discover independent measures that might serve to predict the magnitude or polarity of the CRP changes. Among normal subjects the CRP consistently dropped during each caloric test, probably due to longer periods of eye closure imposed in this group. Recalibration before each caloric test, using an averaging technique, would greatly reduce (but not eliminate) ENG measurement errors.