09-09-2020, 05:41 AM
The Centroid tracking mode calculates the pupil center as the center-of-mass of the blue thresholded area of the pupil. The Ellipse tracking mode calculates a best-fit ellipse around the blue thresholded area of the pupil (seen as a green ellipse on the Host PC), and uses the center of this ellipse as the pupil center.
The Ellipse tracking mode may provide a better calculation of the true center of the pupil compared to Centroid tracking mode when the pupil is partially occluded, such as by the eyelid (as can happen when the pupil is very dilated, or in elderly population with ptosis, or when participants are lying in an MRI scanner).
Note:
The Ellipse tracking mode may provide a better calculation of the true center of the pupil compared to Centroid tracking mode when the pupil is partially occluded, such as by the eyelid (as can happen when the pupil is very dilated, or in elderly population with ptosis, or when participants are lying in an MRI scanner).
Note:
- In Remote mode the Ellipse tracking mode is always used.
- In Head-Fixed mode, the Ellipse tracking mode is slightly noisier than the Centroid mode for the EyeLink 1000. For the EyeLink 1000 Plus and Portable Duo, the two modes have comparable levels of noise.