Fixational eye movements in Tourette syndrome

Area of Science:

• Neuroscience
• Ophthalmology
• Human Physiology

Background:

• Tourette syndrome (TS) is associated with fronto-striato-thalamic network dysfunction.
• Previous studies indicate saccadic eye movement impairments in TS patients.
• Fixational eye movements (microsaccades, ocular drifts) have not been extensively studied in TS.

Purpose of the Study:

• To investigate differences in fixational eye movements between individuals with Tourette syndrome and healthy controls.
• To explore the relationship between fixational eye movement abnormalities and TS pathophysiology.
• To determine if fixational eye movements can serve as biomarkers for TS.

Main Methods:

• Video-oculography was used to record horizontal and vertical eye positions.
• 14 subjects diagnosed with Tourette syndrome participated.
• Data from TS subjects were compared to those from healthy controls.

Main Results:

• Subjects with TS showed reduced microsaccade amplitude and increased intersaccadic intervals, leading to a lower microsaccade rate.
• Ocular drift velocity and variance in eye position during intersaccadic intervals were significantly increased in the TS group.
• These findings suggest impaired ocular stability during fixation in individuals with TS.

Conclusions:

• Altered microsaccade characteristics and increased ocular drift in TS may stem from fronto-striatal pathway hyperactivity affecting basal ganglia outflow.
• Impaired frontal eye field fixation contributes to increased ocular drifts in TS.
• Fixational eye movements represent a potential objective biological marker for Tourette syndrome diagnosis and monitoring.