Automatic detection and removal of fast phases from nystagmographic recordings by optimal thresholding

Abstract Recording of ocular nystagmus during vestibular tests does not measure the true response of the vestibulo-ocular reflex (VOR), because the VOR response (so-called slow phase of nystagmus) is interrupted by resetting saccades (so-called fast phase of nystagmus). In order to extract the real VOR contribution, saccades must be removed. In most of the nystagmus processing algorithms, saccade removal requires a human operator to choose a suitable eye velocity threshold able to separate fast from slow nystagmus phases. In the present report a fully automatic removal system is presented which selects an optimal velocity threshold by computing the VOR frequency response and maximizing its coherence function.