
Data Files
©
2013-2017 SR Research Ltd.
125
4.9.3.5 Saccades
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SSACC <eye> <stime>
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ESACC <eye> <stime> <etime> <dur> <sxp> <syp> <exp> <eyp> <ampl> <pv>
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ESACC <eye> <stime> <etime> <dur> <sxp> <syp> <exp> <eyp> <ampl> <pv>
<xr> <yr>
The start of saccades are reported with a SSACC line, which can be eliminated
with the EDF2ASC "-nse" option from the command line prompt or by enabling
“Block Start Event Output” from the EDF2ASC converter GUI preference
settings. The <eye> is "L" or "R", indicating the eye's data that produced the
event.
The end of and summary data of the saccade are reported with the ESACC line.
This reports the time of the first and last sample in the saccade, and computes
its duration in milliseconds. The X and Y eye position at the start and end of
the saccade (<sxp>, <syp>, <exp>, <eyp>) are listed. The total visual angle
covered in the saccade is reported by <ampl>, which can be divided by
(<dur>/1000) to obtain the average velocity. Peak velocity is given by <pv>.
Optionally, the eye-position angular resolution (in units per visual degree) is
given as well.
All samples that are within the saccade will be listed between the SSACC and
ESACC events for each eye, simplifying data analysis.
4.9.3.6 Blinks
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SBLINK <eye> <stime>
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EBLINK <eye> <stime> <etime> <dur>
Blinks (periods of data where the pupil is missing) are reported by the SBLINK
and EBLINK lines. The time of the start of the blink is indicated by the SBLINK
line, which can be eliminated with the EDF2ASC "-nse" option. The <eye> is "L"
or "R", indicating the eye's data that produced the event. The end and duration
are given in the EBLINK event.
Blinks are always embedded in saccades, caused by artificial motion as the
eyelids progressively occlude the pupil of the eye. Such artifacts are best
eliminated by labeling and SSACC...ESACC pair with one or more SBLINK
events between them as a blink, not a saccade. The data contained in the
ESACC event will be inaccurate in this case, but the <stime>, <etime>, and
<dur> data will be accurate.
It is also useful to eliminate any short (less than 100 millisecond duration)
fixations that precede or follow a blink. These may be artificial or be corrupted
by the blink.