RESUMEN
Since the basal ganglia are thought to have a role in controlling ocular fixation it is expected that patients with parkinsonian conditions would show impaired performance in fixation tasks. Our study examines ocular fixation in patients with a range of parkinsonian conditions (Idiopathic Parkinson's Disease, Multiple System Atrophy and Progressive Supranuclear Palsy). Eye movements were recorded from 44 patients and 50 age matched control subjects during ocular fixation both with and without a visible target. The data for each patient were then characterised in terms of fixation periods and saccadic intrusions (SI). Patient groups exhibited larger and more frequent SI as well as greater displacement from the fixation target. Patients with Progressive Supranuclear Palsy exhibit larger SI than control subjects when fixation targets are visible, this difference is reversed in the absence of a fixation target. Patients with Multiple System Atrophy show increased frequency of SI both with and without a visible target. Our findings show that ocular fixation is impaired in patients with parkinsonian conditions and may prove useful as part of an oculomotor profile to aid with the differentiation of parkinsonian conditions.