In this study we examined how pupil size variations affect data quality in four head-mounted eye trackers — the Pupil Core, Pupil Neon, SMI ETG 2w, and Tobii Pro Glasses 2 — alongside the SR Research EyeLink 1000 Plus desktop tracker. By varying screen brightness to induce controlled pupil size changes, we measured the resulting apparent gaze shifts, accuracy, and precision. All head-mounted trackers exhibited the pupil-size artifact (PSA), with apparent gaze shifts ranging from 0.94° for the Pupil Neon to 3.46° for the Pupil Core. Precision effects were device-specific, with some trackers performing better in bright conditions and others in the dark.
The Effect of Pupil Size on Data Quality in Head-Mounted Eye Trackers
