Eye movements enhance stereoscopic 3D vision

In moving organisms, sensory systems must recover spatial properties of the world from signals continually altered by their own movements. These self-generated temporal signals carry useful spatial information across various sensory modalities, but it remains unclear whether they also contribute to fine visual computations traditionally thought to rely on the spatial structure of the retinal images. In humans, stereopsis estimates depth from differences between the images in the two eyes with extraordinary precision. Yet fixational eye movements continually alter these differences, causing binocular disparity to fluctuate over time. Here we show that stereopsis critically depends on these oculomotor-induced input changes. Using high-resolution binocular eye tracking and gaze-contingent display control, we selectively manipulated the retinal consequences of the differential (vergence) and common (version) components of binocular eye movements. Suppressing eye-movement-induced disparity modulations severely impairs stereopsis, even when retinal image motion in each eye is preserved. Across viewing conditions, the strength of disparity modulations closely predicts performance, regardless of whether they are generated by vergence or version. These findings establish stereopsis as a spatiotemporal process and reveal disparity dynamics induced by eye movements as a critical resource for fine depth perception.