Electronystagmography and Video-oculography

Abstract

　Various eye movements can be recorded using Electronystagmography (ENG) or Video-oculography (VOG). Recently, VOG which allows three-dimensional eye movement recording, has become the mainstream choice for eye movement testing. However, VOG has several practical shortcomings, such as poor recording ability in patients with narrow palpebral fissures, inaccurate recording in the lateral eye position, and the time-consuming three-dimensional analysis. In contrast, ENG is capable of stable recording, accurate two-dimensional analysis, and prolonged recordings, still making it one of the most important means for evaluating equilibrium functions in patients with for dizziness and other balance problems. Nevertheless, ENG testing will also need to be adapted to the digital transformation age in the near future. Next, we discuss the clinical significance of various oculomotor assessments using ENG and VOG. The vestibulo-ocular reflex and visuo-ocular reflex (optokinetic nystagmus: OKN) are both sensed through the central nervous system. The circuit shared between these two reflexes is the velocity storage integrator (VSI), assumed to reside in the vestibular nuclei. The VSI is further controlled by positive cerebellar feedback. Understanding these control mechanisms is one of the most important aspects when interpreting the results of oculomotor evaluation on the ENG and VOG systems. Other eye movements that reflect the functions of the VSI include various types of after-nystagmus (AN). Finally, we discuss the mechanisms of the different types of AN that can be recorded with ENG or VOG.