Objective characterization of square-wave jerks in progressive supranuclear palsy patients and healthy volunteers

Abstract

The eyes do not stay perfectly still during visual fixation. Fixational eye movements and saccadic intrusions continuously change the position of the gaze. Here we focus on the most common type of saccadic intrusion: square-wave jerks (SWJs). SWJs are characterized by one small horizontal saccadic movement that moves the eye away from the fixation target, followed by a corrective saccade towards the target shortly thereafter. SWJs are prevalent in some neurological diseases such as progressive supranuclear palsy (PSP). However, they are also common in normal subjects. We developed an objective algorithm to automatically identify SWJs in PSP patients and normal subjects, during visual fixation of a small target. Our results show that SWJs are common in both PSP patients and normals. However, SWJ rates and magnitudes are larger in the PSP group. Thus the objective characterization of SWJs may provide a powerful new tool in the differential diagnosis of oculomotor disease.

Footnotes

 Supported by: the Barrow Neurological Foundation, the Arizona Biomedical Research Commission, NIH grant EY06717, the Office of Research and Development, Medical Research Service, Department of Veterans Affairs, the Evenor Armington Fund, and the OASI Institute for Research and Care (IRCCS) on Mental Retardation and Brain Aging, Troina, Italy.