Background One of the most promising categories of clinical biomarker in Parkinson's disease is eye movement abnormalities, in particular visually guided horizontal saccades.
Methods odern equipment permits the rapid acquisition of large datasets enabling highly accurate quantification and statistical analysis of saccadic abnormalities. We examined a cohort of 50 PD patients and 50 age and sex matched healthy controls using a portable non invasive infra-red oculometer to record horizontal (a) prosaccades and (b) antisaccades (a saccade in the opposite direction of an abruptly appearing visual stimulus). 420 trials were obtained per patient in less than 30 min. The latency distributions were analyzed using the LATER model and analysis of variance was used to compare the groups. Saccadic tasks were performed in single–task blocks (either blocks of prosaccades or blocks of antisaccades) and in a conflict task in mixed-task blocks (blocks of randomly interleaved pro- and antisaccades).
Results PD patients displayed deficits in the antisaccadic task, with normal latencies in performing the prosaccades but higher error rates in performing an antisaccade than in controls.
Conclusion Measurement of antisaccades may provide unique insights into the mechanisms of oculomotor control and its dysfunction in early Parkinson's disease patients.