title: Directional eye fixation sensor using birefringence-based foveal detection.
abstract: We recently developed and reported an eye fixation monitor that detects the fovea by its radial orientation of birefringent nerve fibers. The instrument used a four-quadrant photodetector and a normalized difference function to check for a best match between the detector quadrants and the arms of the bow-tie pattern of polarization states surrounding the fovea. This function had a maximum during central fixation but could not tell where the subject was looking relative to the center. We propose a linear transformation to obtain horizontal and vertical eye position coordinates from the four photodetector signals, followed by correction based on a priori calibration information. The method was verified on both a computer model and on human eyes. The major advantage of this new eye-tracking method is that it uses true information coming from the fovea, rather than reflections from other structures, to identify the direction of foveal gaze.
authors.affiliation: Krieger Children's Eye Center at the Wilmer Institute, the Johns Hopkins University School of Medicine, MD 21287-9028, USA. bgramat@jhmi.edu
authors.forename: Boris I
authors.initials: BI
authors.lastname: Gramatikov
authors.forename: Othman H Y
authors.initials: OH
authors.lastname: Zalloum
authors.forename: Yi Kai
authors.initials: YK
authors.lastname: Wu
authors.forename: David G
authors.initials: DG
authors.lastname: Hunter
authors.forename: David L
authors.initials: DL
authors.lastname: Guyton
mesh_terms: D005403:Fixation, Ocular / Q000502:physiology*; D005584:Fovea Centralis / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*; D014159:Transducers