A review of computerized electronystagmography technology

A Video-Oculography Based Telemedicine System for Automated Nystagmus Identification

This paper presents the research and results for an automated jerk-type nystagmus identification system that makes use of an efficient, low cost video-oculography (VOG) device, designed for telemedicine applications. The pupil position is estimated by a hybrid tracking algorithm from the captured VOG images. It is also shown that wavelet analysis with an appropriate mother wavelet, coupled with well-defined geometric constraints can provide a reliable and robust nystagmus identification algorithm. Some original research regarding robust analysis for signals with mixed content is also presented.

A wavelet approach for unsupervised nystagmus analysis on ENG and VOG recordings

Several algorithms are available to quantify nystagmus beats in electro nystagmography (ENG) and videooculography (VOG) recordings. These algorithms use parameterized approaches to detect the fast components of nystagmus beats. This paper proposes a wavelet approach to detect fast components of nystagmus beats. The main advantage of this approach compared to alternatives, is the completely unsupervised automated routine. The algorithm is implemented and validated in different clinical experiments. The results are compared to that of an alternative parameterized technique. Results show that the wavelet approach is suitable for automated nystagmus analysis.

Variations in calibration for computerized electronystagmography

The accuracy of the analyses of vestibular test results obtained from a computerized electronystagmography (ENG) system depends on the accuracy with which the system has been calibrated to record the patient's eye movements. The variability of the calibration sensitivity was investigated by analysing the records of 50 consecutive patients who attended for vestibular testing and a study was carried out using 16 volunteer subjects to examine the contributions that time, changes in lighting and subject movement made to this variability. The effect of calibration frequency on the results obtained from caloric testing was also examined by analysing 16 patient records. The mean percentage change in sensitivity between the first two calibrations carried out on patients was found to be -17%, with a standard deviation of 18%. However, there seems to be little baseline drift over time under constant lighting conditions. Changes in lighting have a marked effect, and the adjustment to lighting changes is slow. Gentle movement has little effect. Repeated calibration does not seem to be an effective method to control the calibration-related errors in caloric test results. Careful control of room illumination and the use of adequate adaptation periods to allow patients to adjust to the lighting should help to improve accuracy but, even in the absence of satisfactory calibration, the use of a computerized ENG system can provide valuable diagnostic information.