As Far as Eye See: Vergence-Pupil Coupling in Near-Far Depth Switching

2026-04-02

AI Summary

This study investigates the influence of pupillary-convergence coupling on convergence artifacts in eye-tracking–based depth estimation. Using a beam-splitter apparatus to present real near and far targets, controlled convergence/divergence eye movements were elicited under static, luminance-modulated, and segmented fixation conditions. Combining head-mounted eye tracking, synchronized pupillary-convergence analysis, and an audio-cue paradigm, the findings reveal that pupillary-convergence coupling remains significant even in the absence of visual depth cues. Introducing luminance modulation effectively reduces inter-subject variability and enhances consistency in convergence estimation. The results demonstrate that near and far targets can be reliably discriminated based on convergence angle, and that luminance modulation sharpens the coupling effect, though it does not eliminate it entirely.

Abstract

Vergence is widely used as a proxy for depth perception and spatial attention in immersive and real-world eye-tracking studies. In this paper, we investigate how pupil size artefacts affect vergence estimates during real physical depth viewing with a head-mounted eye tracker. Using a beamsplitter setup with physically near and far targets, we elicited controlled convergent and divergent eye movements under static, luminance-modulated, and blockwise fixation conditions. Near and far targets were reliably separable in vergence angle across participants. However, pupil-vergence coupling varied substantially across individuals and conditions. Static illumination produced large inter-participant variability, while luminance modulation reduced this spread, yielding more clustered estimates. Blockwise and audio-cued recordings further showed that pupil-vergence coupling persists even without visual depth onsets. These results suggest that pupil size fluctuations can systematically influence vergence estimates, and that controlled viewing conditions can reduce--but not eliminate--this effect.

Problem

• vergence
• pupil size
• depth perception
• eye tracking
• pupil-vergence coupling

Innovation

• vergence-pupil coupling
• depth perception
• eye tracking
• pupil artefacts
• head-mounted display