The authors report on the smooth pursuit and saccadic eye movement waveforms elicited from normal patients while viewing standardised calibrated targets. Serial trials were performed on each patient to determine test / retest reliability: nine trials producing 117 results by three different examiners. Patients were assessed by multiple examiners to evaluate intra-examiner variability. Eye movement waveforms were elicited from normal patients (13 patients aged 18 years or older). Five movement characteristics included saccadic latency, velocity and precision, pursuit gain and velocity. Overall test / retest variability was low where the median coefficient of variation (CV) of the three testers for all five eye movement categories was less than 15%, and less than 10% of the CVs calculated were more than 20%. With low test / retest variability the VNG system is considered reliable to produce repeated measurements with consistency when operated by the same person. The authors propose that changes >20% before and after treatment in future study data can be attributed to treatment effect where patients are tested by the same examiner. Significant inter-observer variability was noted due to setup variations. Therefore future studies should aim for the same examiner for all visits.

Reliability and application variability of a commercially available infrared videonystagmography unit.
Gerling A, Leu SY, Morton A5, et al.
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Fiona Rowe (Prof)

Institute of Population Health, University of Liverpool, UK.

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