Estimation of the Cyclopean Eye from Binocular Free Visual Explorations

Abstract

Binocular video-oculography records separate signals for each eye, yet human visual processing and oculomotor control operate relative to a single, virtual cyclopean eye. This study addresses the estimation of the cyclopean eye during binocular free visual exploration, a target-free paradigm widely used for the screening of neurological disorders. Using eye-tracking data collected at 1 kHz from 113 participants across three cohorts (patients with Parkinson's Disease, age-matched healthy controls, and young controls), we compare two different methods: one based on an Independent Component Analysis and another based on Factor Analysis. The extracted cyclopean signals were evaluated on their ability to preserve clinically critical fixation and saccadic events using both velocity-threshold and pixel-dispersion event detectors, and were validated against references via Dynamic Time Warping. Results suggest that the technique based on Factor Analysis guarantees full identifiability across all subjects and achieves low alignment errors, performing comparably to the traditional Version Signal (point-wise mean) while dynamically adapting to inter-eye asymmetry. Furthermore, the second factor in this technique was empirically null across all fitted models, confirming that a single latent factor fully accounts for the shared binocular gaze dynamics. These findings establish Factor Analysis as an identifiable framework for estimating the cyclopean eye in target-free visual exploration protocols.