Definition : Computerized video recorder systems designed to view, record, and analyze two-dimensional (i.e., horizontal and vertical) or three-dimensional (i.e., horizontal, vertical, torsional) eye movements, usually during a set of standardized eye movement tests. These instruments typically consist of goggles or light masks, including an infrared (IR) light source and an IR camera for each eye, as well as a dedicated or standard computer with appropriate software to process, record, analyze, and display the digital video signals obtained from the eye movements (including real-time observation of the actual eye movements) and/or reports related to the eye-movement tests. The human eye cannot detect IR light signals, permitting the performance of tests using invisible light without any additional disturbance. Videonystagmographs (VNG) may include projectors and/or video screens controlled by VNG software to display visual stimuli that may be followed by the patient during the tests. VNGs are mainly used to perform dedicated standard tests (e.g., caloric, positional, gaze, saccades, smooth pursuit, Hallpike, optokinetic) for detecting vestibular conditions (e.g., balance, vertigo, dizziness); they may be used also to detect the presence of drugs as well as multiple sclerosis and other disorders characterized by involuntary eye movement (nystagmus).
Entry Terms : "VNGs" , "Videooculographs" , "Nystagmographs"
UMDC code : 21989