Systematic shifts of fixation disparity accompanying brightness changes

Do pupil-based binocular video eye trackers reliably measure vergence?

“…The vergence angle and the distance to the binocular fixation point are used to investigate depth perception and binocular coordination in vision science (Enright et al, 1987a(Enright et al, , 1987bWagner, Ehrenstein, & Papathomas, 2009;Wismeijer, van Ee, & Erkelens, 2008;Wismeijer & Erkelens, 2009) and binocular coordination in reading (Kirkby, Blythe, Benson, & Liversedge, 2010;Köpsel & Huckauf, 2017;Huckauf, 2018;Nuthmann & Kliegl, 2009). There is a debate about fixation disparity in the literature on binocular control in reading.…”

“…Köpsel and Huckauf (2017) used dark and light backgrounds and were able to replicate the results of both Nuthmann and Kliegl (2009) and Liversedge et al (2006) with a pupil-based video eye tracker (SMI iView X hi-speed 1250). Huckauf (2018) added combinations of calibrations with dark and light backgrounds with dark and light stimuli and report that when the calibration background matches the one during reading, fixation disparity was close to zero deg. Huckauf (2018) concludes that vergence shifts occur as an effect of brightness changes, but cannot rule out that "the effects measured here are only artifacts (or side-effects) of the pupil-size changes reported earlier, nor can it be ruled out that the changes in pupil size are only artifacts (or side-effects) caused by vergence shifts".…”

“…Huckauf (2018) added combinations of calibrations with dark and light backgrounds with dark and light stimuli and report that when the calibration background matches the one during reading, fixation disparity was close to zero deg. Huckauf (2018) concludes that vergence shifts occur as an effect of brightness changes, but cannot rule out that "the effects measured here are only artifacts (or side-effects) of the pupil-size changes reported earlier, nor can it be ruled out that the changes in pupil size are only artifacts (or side-effects) caused by vergence shifts". According to Drewes et al (2014), different lighting conditions affect pupil size and may consequently affect the apparent vergence state in an idiosyncratic way.…”

Development of a Text-Based Communication System with Eye Tracking Technology

“…Owing to the importance of gaze interfaces, various gaze interfaces for text entry have been developed. (1)(2)(3)(4) However, conventional interfaces are just a replacement for a keyboard, which limits the practicality of gaze writing.…”