Multimodal eye-tracking reveals impaired inhibitory control and reduced preparatory pupil dilation in essential tremor

Abstract Essential tremor is increasingly recognized as a disorder involving cerebello-thalamo-cortical and autonomic processes beyond tremor itself. Oculomotor, pupillary, and blink signals provide complementary physiological readouts of these distributed systems, yet they have largely been studied in isolation. Here, we used video-based eye tracking during an interleaved pro- and anti-saccade task to characterize oculomotor performance, pupil dynamics, blink behavior, and trial-by-trial cross-domain coupling in 45 essential tremor patients and 46 controls. Essential tremor showed impaired inhibitory oculomotor control, reflected by increased direction errors, prolonged anti-saccade reaction times, extended voluntary override time, and reduced generation of express saccades. Preparatory pupil dilation was attenuated and constriction timing delayed despite preserved tonic baseline. In contrast, blink dynamics were largely preserved. Trial-by-trial pupil–saccade coupling was also largely preserved, indicating maintained cross-domain coordination despite reduced preparatory autonomic modulation. Exploratory machine-learning analyses suggested that combined pupil–saccade features may capture aspects of clinical heterogeneity, particularly early-onset status, although these findings did not survive permutation testing. Together, these results indicate that essential tremor is associated with selective impairment of inhibitory oculomotor control and preparatory autonomic responses, with preserved cross-domain coordination. Multimodal eye tracking may therefore provide a scalable, non-invasive framework for characterizing the heterogeneous physiological expression of essential tremor.