Transcript Fercho-EM-Fatigue

Ocular Parameters Related to
Fatigue
Kelene Fercho
Circadian Rhythms in the Human
Pupil and Eyelid (Loving et al., 1996)
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N = 24
Studied every 30 minutes over a period
of 24 hours
Pupil diameter measured using a
Fitness Impairment Tester connected to
a PC
Palpebral fissure distances computed
using digitized frame images from video
recordings
Circadian Rhythms in the Human
Pupil and Eyelid (Loving et al., 1996)
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19 hours after beginning the
experiment, dapiprazole hydrochloride
was administered to one eye
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Comparing pupils would give an indication
of sympathetic input to the unmedicated
pupil
When comparing the two pupils, no
circadian rhythm was detected
Circadian Rhythms in the Human
Pupil and Eyelid (Loving et al., 1996)
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All subjects experienced fatigue as evidenced
by frequent blinking and the inability to hold
a point of gaze
Pupil size was not affected by sleep
deprivation
Palpebral fissure showed weak circadian
rhythms.
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Phase of rhythms was found at a mean time of
5:37 PM rather than the expected night-time
rhythm.
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
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Believed eye blinks provide info on the
general level of activity in the rostral
CNS
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Close physical relationship between the
nucleus of the facial nerve and medullary
structures involved in the sleep/wake
process
Midbrain reticular formation structures
integrate ocular activities to some degree
Lack of identifiable external triggers for
endogenous blinks
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
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N = 10 (AF pilots)
Eye movement data collected using
Beckman silver-silver chloride
electrodes
Subjects completed the Crew Status
Check Card and the Stanford Sleepiness
Scale
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
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Subjects reported in at 1 AM.
Study began twelve hours later
Study involved flying a 4.5 hour sortie.
Flight performance was measured by
deviations from assigned heading,
altitude, and speed.
Subjective fatigue measures were taken
before and after the sortie
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
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Performance continually decreased until
the next to last flight segment, but then
decreased after that until the end
Subjective fatigue measures indicated a
significant change in fatigue
Blink rate, blink duration, long closure
rate, blink amplitude, and saccade rate
were all significantly correlated with
error
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
Stepwise regression was used to determine
what EOG measures predicted performance
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Blink amplitude fit R2 = 0.36
Blink amplitude & long closure rate R2= 0.54
Blink amplitude, long closure rate, & blink
duration R2=0.61
Adding saccade velocity, saccade rate, and
peak saccade velocity did not increase R2
Electrooculographic and performance
indices of fatigue during simulated flight
(Morris et al., 1996)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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N = 156 (all diagnosed with narcolepsy)
Used electronic infrared pupillograph
All recordings done in darkness
Subject fixated on a lighted distant
target.
Headrest and lid crutch employed
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Pupillary size of the narcoleptic state
was calculated as a percentage of the
pupillary diameter in the alert state
When patient was alert, pupils were
large and constant in size (5.5 to 8.5
mm)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Authors developed a classification
system for levels of wakefulness
Level 1 – pupils at maximum size,
pupillary waves virtually absent.
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Subject is alert, well rested, and in an
efficient state.
Environment is stimulating
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Level 2 – pupils are slightly smaller.
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Low-amplitude waves of short duration
Subject is still alert, but sharpness is fading
and the mind may briefly wander
Subjects enter this stage when in a
peaceful environment and when inactive
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Level 3 – mild eyelid droop, pupils are
at 85% of their diameter in level 1
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Subjects likely had inadequate sleep the
night before.
Subjects are irritable and concentration is
reduced.
Subjects are tired but deny drowsiness
Alertness is easily obtained if the
environment becomes stimulating.
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Level 4 – eyelids droop, pupillary
diameter is approximately 75% of the
size in level 1
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Pupillary waves are of medium and high
amplitude and medium duration
Subjects admit that they are drowsy and
would like a nap
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Level 5 – severe eyelid droop and eyelid
closure mmost of the time.
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Pupil diameter is approximately 55% of its
alert size
Waves are medium to high amplitude and
medium duration
Major effort is required for the subject to
stay awake
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Sleep was divided into two levels based
on pupillography.
Level 1 Sleep – pupil diameter was 45%
of the size in wakefulness level 1.
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Wave amplitude is reduced and less
rhythmic
Virtually no low-amplitude waves of short
duration
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
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Level 2 Sleep – pupil diameter is 35%
of that found in level 1 wakefulness
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Some high amplitude pupillary waves
Pupil Size and Spontaneous Pupillary
Waves Associated with Alertness,
Drowsiness, and Sleep (Yoss et al., 1970)
Pupillography as an Objective
Indicator of Fatigue (Morad,
2000)
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N = 12
Pupillary recordings were made with an
infrared video device that used the
“dark pupil system”
Stanford Sleepiness Scale (SSS) used
for subjective fatigue measurements
Pupillography as an Objective
Indicator of Fatigue (Morad,
2000)
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All subjects wore an actigraph on
his/her wrist to record hand movement
for 24 hours before the study
Subjects were instructed to sleep at
home the night before the study and
avoid any activity the next day
Each subject completed the SSS and
pupillography in the morning.
Pupillography as an Objective
Indicator of Fatigue (Morad,
2000)
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At 11 PM, subjects reported to the lab
where they spent the night reading or
watching TV.
The next morning, the SSS and
pupillography were administered
Pupillography as an Objective
Indicator of Fatigue (Morad,
2000)
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Actigraph recordings indicated that all subjects had
slept the night prior to the study.
Pupil size was relatively stable during alertness
After the night of sleep deprivation, pupil size was
found to vary with a tendency to decrease
Median value for alertness using the SSS was 2
before sleep deprivation and 6 after
SSS scores and pupillary diameter were correlated (r
= -0.51, p = 0.028)
Pupillography as an Objective
Indicator of Fatigue (Morad, 2000)
Pupillography as an Objective Indicator of
Fatigue (Morad, 2000)
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First to demonstrate a correlation between
pupillary parameters and subjective evaluations
of the subject’s state of vigilance
Authors were able to assign an absolute number
value for fatigue.
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Cumulative variability for fatigue - mean 79.8  65
Cumulative variability for alertness - mean 11.93  7.1
Cumulative variability never rose about 25 in
alertness
Pupillography as an Objective
Indicator of Fatigue (Morad, 2000)
Effect of Sleep Deprivation on Saccades
and Eyelid Blinking (Crevtis, 2003)
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N = 21 (medical students working overnight
shift)
Subjects performed their normal job duties of
monitoring patients in the sleep disorder lab
Researchers used infrared oculography to
collect data for both horizontal and vertical
eye movements before and after the subject’s
night shift.
Effect of Sleep Deprivation on Saccades
and Eyelid Blinking (Crevtis, 2003)
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Subjects were seated in a dark room in front
of a computer screen
Reflexive saccades, voluntary prosaccades,
and antisaccade tasks were executed
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Reflexive saccades – follow target as quickly as
possible
Voluntary prosaccades – look toward target as
indicated by arrow
Antisaccade – Look in the opposite direction of the
arrow
Effect of Sleep Deprivation on Saccades
and Eyelid Blinking (Crevtis, 2003)
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Results for saccadic latencies were mixed
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Reflexive saccade task – 25% of the subjects had
slower latencies after sleep deprivation
Voluntary prosaccade – 10% of the subjects had
slower latencies after sleep deprivation, but 25%
were faster
Antisaccade – 15% of the subjects were slower,
but 15% of the subjects were faster after sleep
deprivation
Effect of Sleep Deprivation on Saccades
and Eyelid Blinking (Crevtis, 2003)
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Blink rate was significantly higher in the
morning after sleep deprivation
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True for reflexive saccade, voluntary
prosaccade, and antisaccade tasks
PERCLOS System
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A measure of the proportion of time that the
eyes are closed over a one minute period
Reflects slow eyelid closure rather than blinks
Drowsiness criterion of the eyes – greater
than 80% closed
PERCLOS measures the proportion of the
time in a minute that the eyes meet the 80%
closure criterion
PERCLOS System
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N = 14
Used actigraph to screen subjects for
one week prior to the study
For the study, subjects were sleep
deprived for 42 hours
A variety of fatigue-tracking equipment
was used (eye blink, brain wave activity,
head movements)
PERCLOS System
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Every 4 hours subjects were required to
perform an hour long test battery and
complete a survey about mood and alertness
PERCLOS was used for eye ratings.
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Video camera, TV, and video monitor were used.
Scorers manually tracked eyelid movements
Eye closure was based on the percentage of
pupil/iris coverage. Blinks were ignored.
PERCLOS System
PERCLOS System
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Results:
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PERCLOS correlated more highly with
performance measure decrements than the
subject’s own rating of their sleepiness
Bout-to-bout and minute-to-minute
coherence for lapse duration for eye
ratings of PERCLOS were well above the
average coherence for lapse duration for all
other technologies (r = 0.875  0.10)