Illuminance and recording of eye movements by electro-oculography

The fluctuation of the d.c. potential of the eye following changes in the ambient level of illuminance is well recognised in the field of ophthalmology. However, the influence of this factor in the recording of eye movements in the oto-neurological clinic has been little investigated. In this study the variation in the d.c. potential was measured for fixed periods of time after subjects entered a clinic environment of known illuminance and after entering the dark. In the short term (3-4 min), the variation in d.c. potential was less than 20% in the 22 subjects tested. Suggestions are made to minimise these fluctuations in the recording of nystagmus and other eye movements.