F019 Eye movements as biomarkers for Huntington’s disease

<h3>Background</h3> Many centres distributed throughout the brain are involved in controlling eye movements. Each type of eye movement has its own distinctive motor, sensory, and cognitive properties. Brain damage in any area can result in manifest, quantifiable changes to the dynamics and/or accuracy of one or more types. Eye movements are therefore a potentially valuable biomarker for brain dysfunction. <h3>Methods/Techniques</h3> HD gene-positive participants and age-matched controls were presented with a range of visual stimuli to assess the quantitative properties (e.g. speed, accuracy, frequency, gain, etc.) of the following eye movement responses: pro- and anti-saccades, self-paced saccades between two static targets, pursuit of a moving target, and the optokinetic response (OKR) to a moving visual field. The stimuli were produced by bespoke software in MATLAB, and eye movements were recorded using an EyeLink 1000 Plus (SR Research). <h3>Results/Outcome</h3> As previously reported, the main sequences of pro-saccades were not significantly different between the two groups, and the anti-saccade error rate in HD participants was much higher. There was a highly significant reduction in the frequency of self-paced saccades over one minute, which did not appear to be fatigue-related. Finally, HD participants often produced abnormal OKR, and the related perceptual consequences correlated significantly with UHDRS Motor scores. Indeed, this anomaly was apparent even in those with a score of 0. <h3>Conclusions</h3> Non-invasive recordings of eye movement responses to relatively short stimulus presentations may provide useful biomarkers of abnormalities that precede overt clinical symptoms. Some of these deficits appear to progress with the disease.