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Journal of Biomedical Optics

Measuring fixation disparity with infrared eye-trackers
Author(s): Maria De Luca; Donatella Spinelli; Pierluigi Zoccolotti; Fabrizio Zeri
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Paper Abstract

Fixation disparity, that is, misalignment of the gaze direction of both eyes, may be observed in static conditions (through standard optometric evaluation) and dynamic conditions (through eye movement recording). A computation method is presented to determine vergence angles and fixation disparity from gaze positions as commonly recorded by infrared eye-trackers when a participant looks at a personal computer (PC) screen. Eye-tracking devices provide gaze position in coordinates relative to the bidimensional screen surface. From these data, vergence angles can be calculated by trigonometric triangulations; fixation disparity is then calculated from the vergence angles. The application of the procedure to the recordings of one participant is described. To control for the effective alignment of the two eyes on the target during binocular calibration, a procedure based on the dichoptic presentation of nonius lines was used. The recordings confirm that computation and the dichoptic calibration procedures ensure reliable measures of vergence and fixation disparity. The usefulness of this approach with infrared recording of eye position is discussed.

Paper Details

Date Published: 1 January 2009
PDF: 8 pages
J. Biomed. Opt. 14(1) 014013 doi: 10.1117/1.3077198
Published in: Journal of Biomedical Optics Volume 14, Issue 1
Show Author Affiliations
Maria De Luca, Fondazione Santa Lucia (Italy)
Donatella Spinelli, The Rome Univ. of Sport and Movement Sciences (Italy)
Pierluigi Zoccolotti, Univ. degli Studi di Roma, La Sapienza (Italy)
Fabrizio Zeri, Univ. degli Studi di Roma Tre (Italy)

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